Masamune just saw his sister Sagiri after a year of her being a shut-in. Headpats are an advanced maneuver for cute imoutos. He needs to take his time.
Masamune has other women in his life. Like his stacked, er, book stacking classmate Tomoe and his editor Ayame.
It was quite the big scene when Masamune got Sagiri to open her door for him in about a year. He discovered she was the lewd illustrator for his light novels and she discovered he was the author she was drawing for.
Masamune didn't make it into her actual room until later. He was prepared for the worst hikikimori scene he could imagine. But it ended up being just a regular cute 12 year old girl's room, with lots of computers and gaming consoles, though.