I feel like their relationship is shifting.
Although not as well executed in the latest chapters (namely tunnel sex arc), I'm actually a huge fan of relationship dynamics that aren't founded on love, but rather something else, for example responsibility, fear of being abandoned, a false sense of safety and so on.
Whenever a BL Manhwa introduced a couple like this, there's always a psychological undertone which I like reading (into lol).
With the way both are acting, I don't feel like it's love in the traditional sense but rather possessiveness and fear of loss.