Reminder that Rin is the older friend of Ruka's brother who took advantage of her when Ruka was a first-year middle school girl (chapter 19). I believe Rin was in the middle of high school or in her final year. So she's all kinds of messed up. This chapter makes her look even worse, which I didn't consider possible.
Rin's age is hard to pin down, at least with just chapters 19 and 41. Definitely in high school. Brother was her first high school friend, she introduces herself as "from R middle school", and there's the line about going through partners in 3 months. Which suggests the two of them met in Rin's first year of high school. But we don't know how long it took for Rin to meet Ruka. The other point is in chapter 19, where Rin talks to Ruka about exams and going to college in Hokkaido, to Ruka's devastation, but we don't know how long they'd been "together". Though I suppose we need to leave time for Ruka to mess around in middle school after Rin left?
Minimum age gap would be early 13 and late 15, maximal would be late 12 and early 18. Bit under 3 years or bit over 5 years, with the younger at the 12/13 cusp.
("early" being not that early -- Ruka and Rin meet in winter of Ruka's first year, so at least half the school year has gone by already.)
last edited at May 8, 2026 10:49PM