I don't know how to put spoiler tag, sorry. It was revealed later that after the war he started to heavily rely on drugs to sleep, sure it show some hints here and there but his fiancee only found out around vol8.
Where did you read the WN? If you still remember, it would really be a great help. With how irritating the SM and her paramour is at the start, it just makes me want to read their downfall.
To think that this is the same guy that easily get distracted by Akutsu's underwear and getting red when teased, Ooyama really had gone far, what a progress. If only Kazuya was like this.
Is it just me or Mami look different now when she was alone? I mean, before, her eyes looks pretty dead that just want to see others to suffer and could make people afraid of her, but now the way the author draw her eyes like, she was genuinely sad?
I understand Kazuya getting nervous, but why does he have to scream? I just hope next time when they are on a date, whether as a client or not, Kazuya overreaction would be lessen or let him act like how he was when he's with Sumi.