Yagate Kimi ni Naru Saeki Sayaka ni Tsuite

Saeki Sayaka has always been an old soul–serious and reserved, preferring to focus on her studies rather than make friends. Until, that is, a romantic confession from another girl in middle school turns her carefully ordered world upside down. Though none of her classes have prepared her for this, Saeki must now come to terms with her sexuality in this gentle, coming-of-age novel about grappling with first love, growing up, and relating to other people.
(Source: Seven Seas Entertainment)