Tenjou No Shita

An ever changing (and unusual) love triangle story, set in modern Japan.
[From Lililicious]:
Uchida is in love with Nakano, but feels like she can’t tell him because she turned him down when he confessed his feelings to her years ago. One day, she sees him with another girl– Kobayashi. The three begin spending time together, Uchida wondering all the while if Kobayashi is in love with Nakano and vice versa. It isn’t until much later that she finds out the true object of Kobayashi’s affections…