Naruto: How does Sakura get the diamond on her forehead

Sakura Haruno is one of the main supporting characters in the Naruto series. As a part of Team 7 under Kakashi Hatake, Sakura wasn't that strong until she started training under Lady Tsunade.

The only other individual to have a diamond mark on their forehead is Lady Tsunade. Had it not been for the latter, Sakura wouldn't have been able to achieve this diamond on her forehead. Lady Tsunade was one of the three legendary Sannin of the Naruto world. Apart from being a powerful Shinobi, Lady Tsunade was also an amazing medic.

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Sakura and the diamond mark in Naruto : Why does she have it, and when?

This diamond mark is a result of the Strength of a Hundred Seal jutsu. While Naruto and Sasuke obtained parts of the Sage of Six Paths' power, Sakura learnt the Strength of a Hundred Seal jutsu, which also happens to predate the Sage of the Six Paths era.

This jutsu is a very complicated one since it requires immense chakra control. Users of this jutsu store vast amounts of chakra in one part of their body, which is usually their forehead for a prolonged period of time. After a certain amount of chakra is stored, it manifests into a diamond-shaped mark on the users' forehead.

Once it is fully manifested, users can then perform any jutsu without utilizing extra energy. When this seal is released, the mark spreads all across the users' faces, distributing the stored chakra throughout the users' body, amplifying their power to a huge extent. Interestingly, this seal never vanishes from the users' forehead, further showing that they can use it as and when they can.

Moreover, this diamond mark is also linked to the ability to summon Katsuyu. Katsuyu is a giant slug that resides in the Shikkotsu Forest. She also happens to be the personal summons of Lady Tsunade and later on Sakura Haruno in Naruto.

Although Sakura never had the seal from the very beginning, she gained this mark on her forehead during episode 373 in Naruto Shippuden. It was only after she gained the diamond mark on her forehead that Sakura summoned Katsuyu and formed the new Three Way Deadlock alongside Naruto with Gamabunta and Sasuke with Manda.

Despite being considered a weak individual, Sakura showed the strength and determination of a true shinobi. During the Fourth Great Ninja War, Sakura was reminded of her younger days when she had to stand behind Naruto and Sasuke during any fight. However, after training under Lady Tsunade and mastering the Strength of a Hundred Seal, Sakura was able to see herself on a par with her allies.

To sum it up, the diamond mark on Sakura's forehead is the mark of the Strength of a Hundred Seal jutsu, that she can use to enhance her physical abilities in combat. Sakura has also managed to find a way to divert some of her stored chakra to her natural reserves, a tiny feat that Lady Tsunade is yet to figure out in the series.