Momose was the best thing to happen to Yashiro. This movie shows how difficult it is to accept when we are different from others and how important it is to have someone eho understands and accept you before you accept yourself. Momo showed Yashiro that he is not wierd or wrong to choose be something other than what society tells him to be. It doesn't matter when he dresses as a guy or a girl, Momo likes him in both his avatar. But he encourages Yashiro to accept himself the way he likes to be and not worry about what others thinks.

Now, yes Momo can be a bit aggressive, but he is a teen who never had a relationship before and doesn't know how to express his love and devotion for Yashiro. He is learning. He even asks Y to tell him how to behave because he doesn't know what is expected oglf him as a boyfriend. He is not a horny teen just looking for a fun time. He is actually attracted to Yashiro as a person. And wants to express his love to him. He comes to strong because On one side he has already accepted that version of Y and Y is still trying to accept both - him dressing as a girl and a guy liking him. Its a lot and needs time to adjust. But if Momo was not strong willed he would not have been able to break down all the insecurities of Yashiro
As some have pointed out that Momo tried to force himself on Y, but He stopped his aggressive behaviour when he saw that Y didn't want it. He was under the impression that it was both sided because Y invited him over. So no I don't think he had any intention of imposing himself on Y. He only thought that he needed to work more to make Y understand his feelings.
This is a very sweet story that shows how important it is to have someone who loves you and acceps you before you even accept yourself and make you fall in love with yourself. Y not only fell in love with Momo but was able to accept his sexuality and lifestyle because he was so naturally and non judgementally loved by Momo.