Sarin (ザーネ, Zāne) is one of the minor characters of Summon Night: Swordcraft Story 2. She is a mermaid who lives in the Subterranean Bay and "aids" the humans to look for an "object to safely area's treasure" to get the said latter. In fact, the "object" was her missing magical comb which enables her to transmogrify into a human and that she needs it badly. She flirts with the protagonist at first, regardless of gender, before eventually falling head-over-heels for Byron. She is also shown to have great sexual appeal in the game (shown in a comical manner).
After Sarin and Byron are finally together at the end of the Subterranean Bay arc, she occasionally is part of the sidequests the player can choose to accomplish. In these sidequests, Sarin and Byron face the problems of their relationship over the most mundane reasons and have the player solve the conflict almost every time.