Why does no one talk about the cheating in Lovely Complex?

Im reading this for the first time. All I had ever heard was good things about this story. Ive enjoyed it for the most part up until this point.

Then all of the sudden Risa cheats? This immediately throws me off and makes me not want to continue this story

I tried looking this up and theres like no one talking about this

Someone please discuss with me lol I am blindsided by this amd do not want to continue the story