@IronicWeeabo Makes perfect sense. First, he's a teen. Despite what alpha fuckboys want to appear to be online, many of us were like that. Weren't you a bit conscious about holding hands with a girl?
Second, in this case she's being blatantly sexual about it. And she's on his bed. He looks at her and her hand is probably not the first thing going through his mind.
And third, it's Japan. Different culture. They don't even shake hands when meeting someone, they bow.