From Shinmakoku Scanlations:

Each time he gets a girlfriend, his childhood friend interferes!

It feels like it would be wrong to pursue this feeling…

Whenever Tomo gets a girlfriend, his selfish childhood friend Hideaki comes between them.
Now that Tomo has a new girlfriend, he’s on the lookout, but nothing happens.
Thinking the lack of intervention strange, Tomo then discovers that Hideaki has a new lover—a man!
Maybe he was just showing off, but Tomo can’t forget how gentle his friend looked when he was worrying about love.

A straight guy easily moved by kindness and affection × an egotistical hottie with a strong desire to monopolize.
They can’t go back to the time when they thought they knew everything—a romance blossoms between friends.