Fairly early on the game and easily missable.
The second time you come across the dodgy store clerk, he'll charge you 100,000 for the bathroom key, at this point you can also buy a tin of cat food for 150
Buy this, take the bathroom key and escape via the bathroom window, as you race down a path chasing Kanae you'll find a cardboard box, choose to look in the box and you'll be given the option to feed the cat... once done and all interactions with the box are done the Trophy should pop.