I disagree about him lacking commitment - he likes the childhood friend, and is actively trying to get closer to her. He deliberately tried to tank dog girl's feelings for him for that very reason. I'd say that's pretty committed.
Also, why should he get with Sayuki just because he knows she likes him? Has there been any indication that the feeling is mutual? I don't understand the mentality some people have where you have to get with somebody just because you can - if you know you don't feel the same way they do, then it's just disrespectful in my opinion.