Honkai Impact 3rd vs BlazBlue
Connection:
Both are sword wielding deuteragonists who are heirs from a powerful family (the Raiden family and the Yayoi family respectively) until tragedy strikes which broke their families apart (Mei's mother died when she was young and her father Ryoma was accused of embezzlement by Cocolia and went on the run which labeled Mei as the daughter of a criminal. Meanwhile Tsubaki's ancestor Ayame Yayoi died which results in the already dysfunctional Yayoi family falling apart)
Both enroll in a military academy (St. Freya High and Control Organization respectively) where they meet close friends who, unknown to them, were clones made by a major villain (Kiana Kaslana and Noel Vermillion respectively) and who they would end up fighting in a bitter struggle in the future
Both utilize radioactive energy (Honkai energy and Seithr respectively) formed by a complex and cosmological space that connects every known world in their respective multiverses together, which supposedly also lacks concept and thus potentially grants them limitless power (The Imaginary Tree and Boundary, respectively)
Both were deceived and manipulated by major villains (Kevin Kaslana and Hazama/Yuuki Terumi respectively) into joining their evil organization (World Serpent and Novus Orbis Librarium respectively) in different circumstances (Kevin promised Mei that Kiana will be saved from being killed from Honkai energy overdose if she joins them, whereas Hazama convinced Tsubaki that Noel stole everything from her and that Tsubaki would need to kill Noel)
Both would eventually return to the good side with the help of someone from the past (Elysia and Hakumen respectively) that enabled them to conquer the darkness from within and join the heroes in their final fight against the villains who at that pointed gained a new power they stole and gained a monstrous form (Deliverance Kevin and Susanoo respectively)
Both would also gain an extremely powerful form that was inherited to them (Herrscher of Origin and Weaving Zero: Izayoi respectively) to which they wield powers of concepts that on the opposite sides (Herrscher of Origin uses the concept of fate and Izayoi controls the concept of death via the Immortal-Breaker technique)
