From Hoshi no Hitomi:
Guy’s mother is dead and he has no father to speak of, so he’s been taken in by the family of another little boy, Simon. The two of them are just like brothers and do everything together. Things start to change when Muriel thrown into the mix. She is intended to be Simon’s future fiancee, but both boys are completely infatuated with her. As Guy falls more and more in love with Muriel, Simon becomes more jealous of him and more protective of Muriel. Guy agonizes over the fact that he is in love with a girl he knows he can never have. At the same time, it’s not completely clear which of the two boys Muriel actually favors.