Valkyrie Drive: Mermaid - Season 1 - Eps 5: Giant Girl, Little Heart
Mirei, Mamori, and Kasumi come across a girl named Nimi Minimi who, after running away from the castle when Charlotte tried to force her and her girlfriend Noe Oya into separate partnerships, somehow wound up in a giant form. Nimi is brought to Atelier Torino, where she manages to get along with everyone despite her gigantic form. The next day, as Nimi suddenly grows even larger, Mamori encourages her to go and see Noe and tell her how she feels. This naturally causes panic as she approaches the castle, with Kasumi's attempts to stop her only causing her to grow larger still. Before Charlotte can attack, Mirei and Mamori break Noe out of detention so that she can reach Nimi, allowing her to return to normal size. Akira then explains that the growth was a cause of Nimi's powers, which had simply taken a while to activate, allowing Nimi and Noe to remain partners with each other.
About Valkyrie Drive: Mermaid

Title: Valkyrie Drive: Mermaid
First Air Date: 2015-10-10
Last Air Date: 2015-12-26
Status: Ended
Rating: 7.1/10 (from 35 votes)
Language: JA
Seasons: 2
Total Episodes: 12
Network: AT-X Tokyo MX Sun TV TV Aichi BS11 KBS Kyoto
Genres: Animation, Action & Adventure
Production Companies: ARMS
Synopsis
Tokonome Mamori is transferred to Mermaid - an artificial quarantine island for people with superpowers. When Mamori is attacked, a newly transferred girl named Mirei saves her. The enemy doesn't stop, however, and the two are soon cornered. Just when they think all hope is lost, Mirei kisses Mamori, and Mamori turns into a sword. Mirei then wields the sword and launches a counterattack against their enemies.
Cast

Yuka Iguchi
Mirei Shikishima

Mikako Izawa
Mamori Tokonome

Yuna Yoshino
Akira Hiiragi

Asami Seto
Charlotte Scherzen

Azumi Asakura
Lady J

Masumi Tazawa
Kasumi Shigure

Yurika Kubo
Meifon Sakura

Hitomi Harada
Momoka Sagara

Saori Onishi
Rein Hasumi

Kikuko Inoue
Torino Kazami