Convenient Semi-Friend, Vol. 1

-What if we became friends with benefits.-- Suuna, a gloomy high school student, leaves home to live in a dorm. But when she nervously enters her room, she finds her roommate, Ruka, feeling up another girl! She finds out Ruka needs a -friend with benefits,- so Suuna takes charge and proposes they form a -(semi) friends with benefits- contract-?