You do realize that Robia cheated on the actual princess not the isekai right? Also the actual princess was a dick she used him and his feelings just so she could have sex with him and in the end she just said literally in front of him. "I wasn't satisfied with what happened/your bad at sex I don't want you here". Not to mention he wasn't even part of the harem yet when this happened. If someone you liked ended up doing this to you and NOT allowing you to exit the relationship (Robia couldn't if he wanted to since the princess is the future empress and all with her being a dick she could kill him) wouldn't you cheat/find someone you actually love?
You do realize that Robia cheated on the actual princess not the isekai right? Also the actual princess was a dick she used him and his feelings just so she could have sex with him and in the end she just said literally in front of him. "I wasn't satisfied with what happened/your bad at sex I don't want you here". Not to mention he wasn't even part of the harem yet when this happened. If someone you liked ended up doing this to you and NOT allowing you to exit the relationship (Robia couldn't if he wanted to since the princess is the future empress and all with her being a dick she could kill him) wouldn't you cheat/find someone you actually love?