Naruto vs Honkai Impact 3rd

Connection:

Both are anti-hero sword welding deuteragonists with lightning based abilities who started off as optimistic prodigies born into powerful bloodlines (the Uchiha Clan and the Raiden family, respectively) but everything changed after a tragic incident that involved family members they were close to, (Itachi Uchiha and Raiden Ryoma, respectively) that involves horrible crimes (Itachi slaughtered the Uchiha clan and Ryoma was arrested for embezzling funds of his company) all thanks to the selfish actions of major villains (Itachi was ordered by Danzo Shimura to slaughter the clan while Ryoma was framed by Cocolia)

These events led to both isolating themselves from the world and led them to becoming dark and cold, that is until they met the series protagonist who are energetic and have monsters inside of them (Naruto Uzumaki and Kiana Kaslana respectively) whom they form a bond with due to similar experiences of loneliness.

Both would also awaken dark powers as a result of what they experienced (The Sharingan and the Herrscher of Thunder respectively), they would eventually meet a third party (Sakura Haruno and Bronya Zaychik respectively) and become members of major squads (Team 7 and Squad V respectively) lead by laidback but chad mentors (Kakashi Hatake and Himeko Murata respectively)

Despite being prodigies both would eventually fall behind the protagonist and started to get saved by them multiple times, this led to them being insecure which gives them a desire to grow stronger, both would eventually follow a dark path after receiving offers from major villains (Orochimaru and Obito Uchiha for Sasuke and Kevin Kaslana for Mei) and join major worldwide terrorist organizations (Akatsuki and World Serpent respectively) this ultimately led to an emotional battle with the protagonist who won't let them stand by their decisions that ended with the deuteragonists' victory and became antagonists from then on.

After being separated for quite some time both would eventually reunite with the protagonists and join them against the villains in large scale world wars, they eventually meet a god like being (Hagoromo Otsutsuki and Elysia respectively) and receive new abilities (the Rinnegan and the Herrscher of Origin respectively) and battle against the big bads of the series who want world peace (Madara Uchiha and Kevin Kaslana respectively), ironically they strongly resemble the dear people who the villains are close to (Sasuke resembles Izuna, Madara's brother and Mei resembles Dr. MEI, Kevin's lover from the Previous Era) eventually after the wars are done both would eventually reconcile with the protagonists and redeemed themselves and years later in adulthood would go on to be the mentors of the new protagonists (Boruto Uzumaki and Adam respectively) while the protagonists are gone (Naruto was sealed in a different dimension by Kawaki while Kiana traveled to the moon)

Additionally they both have dragons in their arsenal (Kirin and Kurikara respectively)