Makimodoshi no Koi no Uta

Minoru is Riko's first boyfriend and first love, but to Minoru, Riko is his second girlfriend. Even worse, it seems that Minoru still cares an awful lot about his ex, whose sister actually goes to the same school as Riko and Minoru. Then one day the pretty boy of the school, Sakashita, shows he's interested in Riko by kissing her on the lips! Can things get any more complicated?

(Souce: Fateful Encounters)

Included one-shot: linkKarakuchi Ouji ni Goshuushin! (Liking a Poison-Tonguer Prince!)