From Lilac Scans:

"The two of us won't be able to break this relationship for the rest of our lives."

After a certain incident, high school student, Sakaki, has in essence, been made to follow everything his friend, Nishi, says. Although he has accepted this matter, Sakaki still feels somewhat down about it. While Nishi wants to continue having Sakaki all to himself, Tachibana appeared between them. Tachibana seems to want to get closer to Sakaki however...

This is a triangle love story of heaping feelings...