Berserk, Vinland Saga, and Vagabond are three seinen series that are absolute fan favorites. Hardly anyone has anything bad to say about any of these three manga series, and for good reason.
Seinen is a genre of manga that is targeted towards young adult men. While they are much more distinguished than shonen manga, they do share similarities with it. However, the differences happen to outweigh the similarities as they focus on action, science fiction, fantasy, politics, relationships, comedy, and sports.
Berserk, Vinland Saga, and Vagabond depict inspiring stories of men finding the light in the darkness
All three manga - Berserk, Vinland Saga, and Vagabond are mostly focused on their protagonists, namely Guts, Thorfinn, and Musashi, respectively. All three have had a terrible past filled with trauma and mistakes, but they decided to get their lives back on track.
Their true goal isn't to attain a position of power, title or wealth, but to become a good person by being kind to others as they discover it to be the strength of their well-being.
They are focused on bettering themselves and are not driven by others' goals and statuses, which is why they are loved by fans as they get to witness their development with each passing chapter.
These three stories show the gray areas of the world as they depict how the world isn't truly dark or light. While their lives had a truly dark time, the three protagonists are trying to find the light from within as beauty and inspiration can be found even in one's darkest times.
A character does not necessarily need to have a good start but needs to develop over time. This is exactly what pulls fans to read Berserk, Vinland Saga, and Vagabond, as all three manga depict the stories of men who had broken childhoods filled with abuse and torment and realized they should become better if they have to turn their lives around.
Their stories even have realism to them, as all three characters were shown to have an evil side. This evil did not come from within but from their surroundings.
However, they did not blame others but started working on themselves to show accountability for the terrible sins they committed in the past. Thus, similar to real life, the protagonists aren't left unpunished and are held accountable for their actions by themselves and society.
Moreover, the stories did not depict a good ending for every character. The manga creators know that a good ending for one character could mean a bad ending for another, and that is clearly depicted in these mangas, making them much more compelling for fans to read.
Moreover, Berserk's Guts, Vinland Saga's Thorfinn, and Vagabond's Musashi are actively shown to develop and be shaped by the people, world, and the events around them, which is a clear sign that they are transitioning from rash young teens to rational and peace-seeking adults.
Stories with such a good blend of realism often attract audiences as they too identify the highs and lows of their lives and want to work on them. However, not everyone is able to take that first step.
When one reads such manga, they get that much-needed push towards a better life, which they could not have achieved until they adapted themselves to such a "sigma-esque" lifestyle.
Considering that Berserk, Vinland Saga, and Vagabond do depict such lifestyles, they instantly strike a chord with their audience.