Honkai Impact 3rd vs BlazBlue
Connection:
Both are stern, mature and intelligent swordswomen hailing from iconic video games who are prodigal daughters that came from a strong bloodline (Schariac/Kaslana household and Yayoi family respectively)
Both wield an extremely powerful weapon (Black Abyss White Flower and Sealed Armament: Izayoi respectively) which had been used by their previous owners (Durandal's biological mother Cecilia Schariac and Tsubaki's ancestor Ayame Yayoi) during a war (Second Eruption and Great Dark War respectively)
Both possess several forms with on using their weapon (Durandal has Palatinus Equinox and Tsubaki becomes one with the Izayoi itself)
Both attend a military organization/government that spanned the entire world (Schicksal and Novus Orbis Libararium/NOL respectively) and become one of their highest ranking members (Durandal is an S-Rank Valkyrie and Tsubaki is ranked First Lieutenant) as well as being a member of their elite division (Immortal Blades and Squadron Zero respectively
Both would serve the organization's leader (Otto Apocalypse and Hazama/Yuuki Terumi respectively), not knowing they were the major villains of their series who plotted in the shadows and orchestrated certain events
Both would serve as one of the main villains of their series that fought the white haired protagonists several times (Kiana Kaslana and Ragna the Bloodedge respectively) but eventually rebelled after an event involving their minds with someone to help them (Durandal eventually regained her lost memories and identity as the real Kiana Kaslana with the help of Rita Rossweiss. Tsubaki broke Izanami's curse with Hakumen's encouragement and making contact with Jin's Power of Order) and joined the heroes in their final fight
