The kiss isn't fanservice window dressing, it's the entire mechanism of power. Mamori transforms into a weapon the moment Mirei actually commits to her, and the show never pretends that's anything less than romantic. You're watching two girls save each other by loving each other, framed as sci-fi action instead of apology. The ecchi isn't separate from the story; it's the story. Not everyone signs up for that level of commitment to the bit, and the show doesn't care if you don't.

Sixteen-year-old Mamori Tokonome is kidnapped during gym class and wakes up on Mermaid, one of five artificial islands used to quarantine people with superpowers. Soon after arriving she is attacked, and a fellow newcomer named Mirei Shikishima comes to her rescue. The enemies refuse to back off, and the pair end up cornered. With hope running out, Mirei kisses Mamori, awakening her Exter ability and turning her into a sword that Mirei wields to strike back. The island holds many possible allies and rivals, including the sadistic Charlotte, the crafty Meifon, the charismatic Akira Hiiragi and the biker duo Lady Lady. The show mixes action, fantasy, sci-fi and romance with heavy ecchi content.