Whose hands are these in Assassination Classroom chapter 179? In chapter 179 of Assassination Classroom, there are 2 panels showing hands holding each other:



My hunch is that there's no distinctive evidence (unless there is some from the anime or movie or something) as to leave it perhaps to the reader to interpret as they like to avoid backlash. Though I feel there have been a fair amount of hints pointing towards Kayano and Nagisa if I got the names right (Kiss, valentines, the poster in the top left panel is of her). Though there could be evidence against it as well that I am not aware of.

Whose hands are these?
The poster and the scene afterward featuring Kayano strongly implies the female hand is hers.

It would sense that the person she was holding hands with someone that wasn't present at the old classroom building at the time, assuming that all the vignettes were happening more or less in real time.

The most likely conclusion would be that the male hand belongs to Nagisa.

After being questioned by Hara, Kayano didn't deny that they weren't together, and only mentions that he's focusing on his teaching career.

The anime skips this scene so there is no decisive conclusion, only speculation.