I never said they never make out or what what I'm trying to say is from the adaptation it would take a long time before they get that part. From what I remember after the ranking update the other S class little girl would visit him and ask for help as they are trying to solve the rift. (The little girl knows he J)
He will also help with the ML in uncovering the crime shown in chapter 1. After that they will focus on looking for the rifts.
If you want I can summarize what I can remember but this is what I call a slow burn.
I don't think they kiss and tell right away considering ML was the child save by J
Comments below mine are so funny.
Just a spoiler if y'all want, no this is slow burn and it took some time before they got this sorted out. If I remember correctly ML kiss MC once and never did it again coz the MC that time puked some blood. mL assumed it was due to his poison but it was not.