One possible plot could be Deku finding out his partner cheating through overhearing a conversation. He might be heartbroken and initially go into denial.
Perhaps Deku discovers evidence of the cheating like text messages on his partner's phone. This could lead to him confronting his partner and a big emotional showdown. He might then isolate himself for a while, feeling betrayed and losing confidence in himself and relationships in general.
In some versions of this fanfiction, Deku's friends could find out about the cheating before he does. They then have to figure out how to break the news to him. This could lead to some internal conflict among his friends about whether to tell him or try to handle the situation themselves. It also shows how Deku's relationships with his friends are affected by this betrayal in his romantic relationship.
One possible plot could be that Issei discovers his partner cheating through finding love letters or messages from the other person. He then goes through a phase of heartbreak and self - doubt, questioning what he did wrong.
He might cry a lot. Deku is very emotional, and being cheated on would be a very painful experience for him. He could also get angry, which is rare for him, but this situation would be so unjust that he might not be able to hold it in. He'd probably start to question his self - worth too, thinking that there was something wrong with him that made his partner cheat.
Well, in this type of fanfiction, perhaps the plot unfolds with Naruto coming home early one day and catching his girlfriend in the act with another person. This discovery could send him into a downward spiral of self - doubt and anger. He might then go on a journey to rediscover himself and his worth, distancing himself from his old life and relationships. Or, it could be that the girlfriend tries to deny the cheating at first, causing more drama and confusion in Naruto's life.
One possible plot could be that Naruto discovers his partner has been cheating with someone from another village. This could lead to a lot of inner turmoil for Naruto, as he might question his own self - worth and his ability to judge people. He could become more withdrawn and focus solely on his ninja training to numb the pain.
One possible plot could be that Deku is mind - controlled to fight against his friends. His friends then have to figure out a way to break the mind control without hurting him. Another plot might involve the villain using Deku's mind - controlled state to gain access to secret hero information.
Well, it could also be Harry who is wrongly thought to be cheating on his partner. In the fanfiction, perhaps some false rumors are spread by his enemies. They create a situation where his friends start to doubt him, and his relationship is put under great strain.
One possible plotline could be Naruto's initial shock and disbelief. He might go through a period of self - doubt, wondering what he did wrong. Another could be his journey to find himself again after such a betrayal. He might focus on his ninja training more intensely to distract himself from the pain.
Well, one possibility could be that Naruto discovers that his friends have been secretly working against him in some way, like lying about their intentions or using him for their own gains. Maybe they've been making deals behind his back that go against what he believes in.
He might also become more reserved in future relationships. After being cheated on by Anko, Naruto could be more cautious when it comes to getting close to someone again, always having that fear in the back of his mind that he could be betrayed once more.
Naruto might be heartbroken. He's a very emotional character, so he could cry a lot and feel a deep sense of loss.