After the first few pages, I actually thought this might be a manga based on 女神なんてお断りですっ... That's an untranslated LN series about a reincarnated princess named Tia (in her past life, Satia) who led a rebellion and killed off her royal family before ending her own life at the age of 15. But she...
I gotchu...
"Sorry to keep you waiting. We finally get to sleep together..."
"Yeah, we finally get to sleep together...wait... the heck are you saying!?"
"It makes me the happiest when I get to plop into bed with you, Saito."
"Are you okay!? Did you eat something strange!?"
"If I had to say... I...
I just checked a Japanese dictionary. Despite Yamada's assertion, the word he used does, in fact, refer to both necklaces on humans and collars on animals. 🤔
(He said 首輪 (kubiwa) and she corrected him with チョーカー, literally the word "choker" borrowed from English.)