my guess is that he wants to stand on his own feet first. graduate, get a job and become equal to his bf, maybe tell the family about them, and only then move in tho sometimes this author goes with really unpredictable reasoning lol so my guess can be completely off the mark
art is amazing i looove it i can sell my soul to the artist, BUT HOLY FUCK THAT DONG IS LIKE 35CM LONG i was terrified ever since that panel