The interesting part of watching Kaoru and his mother is seeing how much traditional or conservative families never really say things directly. There are things both of them wanted to say but they hesitated and changed the subject. With that, a lot of the time you have to really read the body language and tone things are said to understand the subtext or read between the lines. I also noticed that with his dad - but I felt that for the dad, he didn't want to say anything negative about Kaoru's mom. I think Sen acted more as the voice of direct reason rather than 'the magic pixie trope' otherwise not only would have Kaoru gone but he wouldn't have let himself open up the way he did.