*Hitomi - Yomi: Yomi's Theme are like Western & has straight long hair, yes?
*Christie - Miyabi: White Hair
*Helena - Haruka: Ojou
*Tina - Katsuragi: All of them
*Rachel - Daidoji: Duh... Being a Residents' Big Girls who has a Superhuman Strength
*Leifang - Ryobi: Her BFF with Hitomi that's why
*Nyotengu - Murakumo: Masked Warriors
*Kokoro - Yumi: Kimono Beauty
*Marie Rose - Mirai: A-Cup
Mila cosplays Hikage because of having a same seiyu, yes?
Foreshadows in DOA6:
*Kasumi & Momiji has a same Nice Girl traits, yes? Implied to be BFF since their clans are allies for many generations. Has more BFF parts than rivalries, unlike Asuka & Homura
*Ayane & Honoka are related to Raidou because Ayane is his daughter & Honoka has the same power as his. Honoka implied to be Raidou's other daughter and making her Ayane's younger half-sister, if yes, yet sensing her goodness is too weak to handle that kind of power, Ayane is a perfect candidate to watch over Honoka, or else she'll end up like Raidou. This also recalls what Kasumi used to, doing the right thing instead of following Mugen Tenshin's order, even it risk her life ended up being rogue ninja in order to save/avenge Hayate & apparently kills Raidou, thus decide follows a bit of her footsteps. That's why they've cosplayed as Yagyuu & Hibari.
*Phase 4 wants to be Human, yes? Cosplaying as Ikaruga is the best way to assume new identity, start her new life, changing her appearances, mostly dyes her hair to black & cut short, even changing fighting style to make her more different than Kasumi.
*Lisa cosplaying as Rin makes things 100% that she survived the destruction on offshore. Both were supposed to be dead when sacrificing their lives helping heroes against villains & revealed to be alive.