Seohyun: Sailor Mercury (水野 亜美 Mizuno Ami)

Ami Mizuno is a quiet bookworm in Usagi’s class. Highly intelligent, she serves as the “brain” of the group and can transform into Sailor Mercury, the Soldier of Water and Wisdom, who can generate and manipulate water in all its phases. Ami’s shy and practical exterior masks her liking for pop culture and romance novels. She has a passion for knowledge and taking care of the people around her.

(Click here to Chibi source)