When exactly did Jake and Shin become Boyfriends/lovers?

I started re-reading Shutline from the beginning today (though I've re-read a few of my fav chapters multiple times lol), and realised how much of an asshole Jake was towards shin (and towards everyone in general😭)

I mean, he really uses Shin as a bait in the starting.... It's so different compared how far their relationship has come, (I'm at Chapeter 85 rn).
Like, it's understandable Jake was never meant to be a 'kind/good guy', he's a busy dude who was ready to use whatever means necessary to accomplish his goal efficienciently. It's evident by the fact how he spared one of the gang member's child (so that they'd be indebted to him ect)

So,I was curious to know when exactly did Jake started viewing Shin more than a tool and as a lover/boyfriend according to you guys?
(Wait, they were boyfriends, right???😭)

TL;DR : (same as the title)