For every anime with a large-scale event that radically alters the universe, more than a few series have smaller-scale events that ripple outward. From Light Yagami finding the Death Note to Usagi meeting Luna, smaller events can have an immense impact on the story and the universe of that anime.
The larger effect can be someone becoming a superhero, turning into a mass murderer, or any number of things that result from even the smallest act of kindness or cruelty. As such, this article will look into 10 of the smaller, more intimate events that greatly affect the anime stories and their respective universes.
Disclaimer: All of these anime are subject to spoilers, warnings included. The opinions therein are subject to only the author's opinions and barring one exception only one event per anime.
10 small scale events, like two characters meeting, that greatly affected anime universes
1) Izuku Midoriya gains One for All (My Hero Academia)
The superhero anime world of My Hero Academia practically revolves around Quirks, or superhuman abilities that individuals possess. Because of the proliferation of Quirks and superheroes, society has shifted into a superhuman one where Quirks are considered normal since 80% of the population has one. Enter Izuku Midoriya, who always wanted to be a hero but was born quirkless.
Risking his life attempting to save Bakugo from a villain gained the attention of the Number 1 Hero, All Might. After dispatching the villain, Izuku was given the opportunity of a lifetime - inherit One for All and train under All Might to become a hero. It may be a small event in the grand scheme of things, but it radically altered Izuku's life and started him on the path to becoming a superhero.
It was likewise a secret, hence why it's on this list. Izuku becoming One for All's bearer ended up saving many lives in the series, and it started with him running to save Bakugo. It took real courage to run forward when everyone else was frozen, which was why All Might chose Deku over Mirio.
2) Light Yagami picking up the Death Note (Death Note)
Freak accidents in anime happen almost all the time. People running into each other, car accidents, and natural disasters are among the many events in anime that end up affecting the grand scheme of things. So, what happens when the son of a police detective finds a strange book on the ground and learns it gives him the ability to dispense death on a whim?
Light Yagami was a regular student before picking up the Death Note in the titular anime. While he had already started forming his own sense of justice and morals, the Death Note allowed him to dispense it on a wide scale. It started with a couple of criminals that got off on a technicality and soon spread to FBI agents, Interpol, and eventually worldwide chaos.
Strictly speaking, the power of the Death Note didn't come to Light by divine providence from the shinigami Ryuk. The latter simply dropped it on the ground and waited for someone to pick it up, and that someone just happened to be Light.
3) Yusuke Urameshi saving a kid from a car (Yu Yu Hakusho)
Saving people at the cost of one's life is usually seen as a good thing in anime. Yu Yu Hakusho was no exception, as it granted delinquent Yusuke Urameshi a second chance. Tackling the kid from out of the way of a speeding car may have killed Yusuke. However, as Botan stated, the kid would've lived if he got struck, and Yusuke wasn't supposed to die that day.
So, rather than condemn Yusuke to the beyond, Koenma gave him a second chance, which entailed him becoming a spirit detective to help solve cases of souls not moving on. This eventually gained Yusuke his life back and had him lock horns with Kurama and Hiei, eventually stumbling into Genkai's teachings and the Dark Tournament.
To think all that was from trying to save a kid's life, it goes to show that good deeds can come back around to the person who did them. This changed not only Yusuke but also his rival Kuwabara, making them both better people as a result.
4) The creation and discovery of Stand Arrows (Jojo's Bizarre Adventure)
This was more of a background event throughout every part of JoJo's Bizarre Adventure since Stardust Crusaders, but it still had a major impact on the universe. To summarize, following Dio's defeat at the hands of Jotaro Kujo, Jotaro and Jean Pierre Polnaraff started investigating where and why Stands came to be.
It was discovered that a meteorite slammed into what is now Cape York, Greenland, 50,000 years ago. In 1978, a mineral extraction team uncovered a virus that only seemed interested in completely eliminating all life. Certain people possessed abilities that enabled them to survive exposure, granting them Stands. An unknown man took some of the rocks and fashioned them into arrowheads, which was lost to time until Diavolo uncovered six of them in 1986.
The arrowheads were eventually stolen by Diavolo, with five sold off to Dio's henchwoman, Enya the Hag. These arrows helped push Stands across the world, from the sleepy town of Morio in Diamond is Unbreakable across Italy in Golden Wind and even the Stone Ocean prison. They proved a real headache for the Joestars and the Speedwagon Foundation.
5) Shinichi Kudo getting drugged (Detective Conan)
The experimental and lethal poison APTX 4869 was meant to be quiet and undetectable when used by the mysterious Black Organization. The poison was used in several instances. However, it remains in an incomplete state because several of their researchers either got killed in a fire in the case of Shiho Miyano's parents or defected from them as Shiho eventually did in an attempt to kill herself with the poison.
Shinichi Kudo was just in the wrong place at the wrong time at the start of the anime, trying to pursue two men in black, and got caught witnessing a blackmail transaction with a weapon smuggler. He eventually got knocked out and poisoned, but the strangest thing happened. Instead of killing Kudo, the poison reduced him to the size of a six-year-old.
The same also happened with Shiho, which turned her into a young girl. Although they retain their adult minds and personalities, the characters are just in younger bodies. It was quite the stroke of luck that ultimately led to many murder cases being solved. It helped that Conan (the alter ego of Shinichi Kudo) was taken in by detective Kogoro Mouri and his daughter, Ran Mouri, even if that meant having to repeat first grade.
6) Orochimaru places the Curse Mark on Sasuke (Naruto)
This particular anime entry was a tough choice between Naruto receiving kindness that stopped him from becoming as cold-hearted and murderous as Gaara, Sasuke's departure from Konoha, or Orochimaru's manipulations in the Chunin Exams that led to Sasuke's departure. The third event, while smaller, had more ripple effects on the characters and the anime's story.
Sasuke had always had problems regarding teamwork and getting along with Naruto. It was mending during the Land of Waves, only for Orochimaru's manipulation and Curse Mark to bring all of it crashing down. Not only was Sasuke limited due to the Curse Mark, his own arrogance and insecurity began to take hold when Naruto defeated Gaara. Add on his encounter with Itachi, and it was all set to the blow that led to his departure.
While Sasuke had Itachi on his mind, even as early as the Land of Waves, several incidents, including being a part of Team 7 and doing well in the Chunin Exams, took priority. However, Orochimaru infecting him derailed all that and set Sasuke down his path of vengeance, no matter who stood in his way.
7) Goku bumping his head/being run over by Bulma (Dragon Ball/Z)
One of the most famous examples of an anime journey starting was Bulma nearly running Goku over with her car in the original Dragon Ball anime. This incident had Goku and Bulma meet, and the rest was history as they decided to journey together to collect all seven Dragon Balls. However, further back into the narrative was Goku being adopted by Grandpa Gohan.
Much like how Superman was found and raised by the Kents in Smallville, Goku's crashed pod was found by a wandering man named Gohan. At first, the Saiyan was violent and ill-tempered until one day, he fell down a ravine and hit his head. He was sent into a coma and suffered long-term amnesia. Following this, Grandpa Gohan raised the young boy until his untimely death via Great Ape Goku.
These two events may have been small, but they kickstarted Goku's journey to become Earth's defender. Were it not for him bumping his head, he probably would've been just as bad as Raditz. Hence, everyone within the Dragon Ball fandom is thankful that didn't happen for obvious reasons.
8) Usagi helping Luna (Sailor Moon)
Helping animals is definitely a good thing, especially if they're being bullied. One day, Usagi Tsukino was late for school when she decided to take a different route. This involved saving a cat with a crescent moon mark on its head and berating away kids that were bullying it in Sailor Moon.
It turns out that was no ordinary cat, but a sentient, talking cat named Luna who granted Usagi the ability to become Sailor Moon, the warrior for love and justice. This took a while of Luna stalking Usagi, following her home and then being in the right place to save her from a Youma that had taken over Naru's mom. Thanks to this, Sailor Moon was born and started fighting against the forces of evil.
The same could also be said of meeting the other Senshi, which included saving Ami Mizuno from a cram school trap, Makoto helping Usagi fight off three bullies, or Rei Hino and Usagi's explosive relationship starting when they met. As such, a small act of either kindness or just being friendly led to the formation of the Inner Senshi.
9) Yugi completing the Millennium Puzzle (Yu-Gi-Oh!)
When the Millennium Puzzle was given to Yugi Moto in the Yu-Gi-Oh! anime, it was assumed that it was just a puzzle box that was impossible to solve. Solomon Moto, Yugi's grandfather, originally discovered it in the tomb of Atem and owned it since the 1960s. Yugi himself spent eight years trying to solve it.
When it was finally solved, the spirit inside the Puzzle awoke and took over Yugi's body. In these early times, the protagonist would be possessed by Atem, who'd usually help out against bullies, gangsters, among others who tormented Yugi and those he cared about. It wasn't until the Duel Monsters arc that Yugi would be aware of Atem, called Yami Yugi at that point.
The ripple effects of completing the Puzzle included saving his friends' lives multiple times, thwarting the often lethal efforts of Seto Kaiba to defeat him, and beginning the process of uncovering the mysteries of the other Millennium Items. It also led to many card games with ludicrous stakes, such as the fate of the world.
10) Ash waking up late and getting his Pikachu (Pokémon)
Sleeping in is great, but not when it leads to you being late to start a journey across the known world like how Ash Ketchum started in the Pokémon anime. Whereas in the games, the player character often gets to choose between three Pokémon, the anime's protagonist was too late and was forced to settle for a rambunctious Pikachu.
The two didn't get along at first, to the point where they both nearly got severely injured on the road to Viridian City, with Pikachu gravely in need of care and Ash forced to steal Misty's bike. There, the trio met up again and went up against Team Rocket for the first time in a Pokémon Center.
The rest is anime history, as everything that happened afterward can be traced back to Ash getting a Pikachu that he only got from being late. This event may have been small but had a massive impact, as the duo would be inseparable from there on.
To reiterate the point stated in the beginning, sometimes the smallest of events can have major consequences. A chance encounter, a curse placed upon someone, and getting up late are but only a couple of examples that fit these 10 small anime events that had major consequences.