@MonsieurQuack Not this one, you're forgetting about chapter 31 with "An international student from Germany, thinking that it was normal for a man and a woman to enter the sauna together like in her home country, follows the boy she's interested in into the bath at her homestay and stares at him silently while changing."
@chikinwnag - Yes, kotatsu is a hybrid of table, heater and a blanket.
The heater element is protected by a grate so you can't touch it directly.
From personal experience, contact with any other part of the heater is survivable. But I think kotatsu should have a grate that is better thermally insulated than the outer surface of the heater.