Ya, I am in a spot where I don't really care about Summer - I've never been a big fan of stories that try to put the MC in a relationship in "the past" leading into the story and then re-introduce them later in emotionally impactful ways and the reason is two fold -
1.) There's no guarantee the player is going to find the girl attractive, potentially making the impact of her return meaningless
2.) There's no guarantee the player is going to form any kind of emotional attachment to that character based on just the backstory.
And just as you said, because of the MC's backstory, he'd be written to have this huge emotional reaction to such an event that the narrative would likely spend a lot of time on possibly affecting relationships that the player had begun working on, and the whole time I'd be waiting just to get through it so I could get back to the story I'd actually become invested in with other present-day characters.