By the evening of day 69, when things were at least reasonably under control, Heiji was pretty tired. And while he did want to just fall asleep on the nearest flat surface, wasn't this the perfect opportunity to actually enjoy what they could while Zero still didn't have full control of the warehouse?

Answer: Yes.

A: Gutting a fish, setting up campfire stuff
The last time he'd been allowed into the maze with Hershel, they'd both regretted the lost opportunity. A whole fish tank room full of fish, most of them the kind that were actually supposed to be eaten rather than looked at. And they were going to die soon, anyway, right? Without power.

So technically just leaving them would be terribly wasteful and tl;dr Heiji was carrying a giant floppy wet salmon in both arms over to the river where he was going to (in theory) gut it and scale it and cook it because you know what, he wanted some actual food.

B: Campfire dinner
After a great deal of effort and setup, the smell of cooking salmon began wafting over the garden; once it was near to done, Heiji would start contacting people over the bracelets to tell them what was up and to bring any food or supplies they wanted if they'd found any. Who knows, maybe someone'd find some vegetables they could cook or something.

C: Reading mystery novels/textbooks/language guides
After dinner was over, Heiji was just going to set down with a stack of books and start reading some mystery novels, maybe offer to read something he'd found in the library with someone. HE MISSED READING OKAY, it was his life.

D: Music room
And of course now that the music room was temporarily open, Heiji was looking everywhere for Snake to hopefully listen to some piano playing for real. ...Although he wasn't above trying it out for himself, as well as the other instruments. Or maybe just shredding some cloth in here for bandages.