This is a cookie-cutter shoujo romance story that has been done before, and done better.
To put it simply: Girl has a boyfriend that she claims she loves. Girl meets another boy. Girl befriends boy. Boy has hots for girl, but girl decides that he just wants to be friends (or pretends not to notice). Girl and boy get along like a house on fire, and girl confides her most intimate secrets with boy, secrets she should be confiding in her female friends, if not her "boyfriend." Girl spends more time with boy "friend" than her "boyfriend," having fun, going on dates, going to the beach, going out to eat, doing things she should actually be doing with her "boyfriend."
If it was only once or twice that girl did inappropriate things with her boy "friend" (or the boy "friend" did innappropriate things with her, such as giving her a hicky), it might have been tolerable. But, no, chapter after chapter after chapter she continues to betray the trust her idiot "boyfriend" mistakenly places in her. Girl has no capacity to learn from her mistakes, even though, by the end of each chapter, she actually acknowledges what she has done wrong, but has forgotten her lesson by the beginning of the next chapter.
Don't get me wrong. Girl's love for "boyfriend" never wavers, nor does she ever respond in kind to the repetitive romantic advances of the boy "friend." However, she does seem to worry and be overly concerned about hurting the feelings of the boy "friend," yet seems completely insensitive to how her "boyfriend" will feel is she spends most of her free time with her boy "friend" doing the things she should be doing with him instead. Of course the "boyfriend" knows that the boy "friend" has romantic feelings for his "girlfriend" and is trying to steal her away.
The "boyfriend" is at fault too, as he should have either put his foot down with his "girlfriend" when it became clear what the situation was with the boy "friend," or, my preference, he should have kicked the "girlfriend" to the curb since she obviously can't correct her behavior.
Perhaps the one thing that irritated me most was when, after becoming friends with the boy "friend," the "girlfriend" says to herself, "I've made my first male friend." What the f#$k, b*&^ch, wasn't your "boyfriend" your first male friend? Haven't you been childhood friends with him since kindergarten? What a #^%$!