I do believe the hero loved and loves the MC, but his constant battles made him just focus on defending human race. Of course, everybody has moments that feels sad and recall nostalgic moments in their childhood.
The thing is that, the hero is not dense, he was told by everybody that he loves the MC and will have to live with her that he considered that to be his life until now.
He is experiencing new things but still misses his family and friends, but never gave more thought about it since that is what he knew.
That is why the phrase, you don't realize what you have ubtil you miss it. Since he found another person that is showing the same affection that his childhood sweetheart, he probably thought that she was the one. Remember he went thru so many things and was a different person and won't be liked by people in The past but this companion is able to see that Good in him and is always with him.
Yes a bit selfish and selfless because the MC could have been scared of him or dislike him because he was not the innocent child she knew or still love him. It could have gone either way.