@Oran silvester the story doesnt present mincheol's loan as something he used for a clear legitimate purpose. Mincheol used the loan mainly to cover immediate financial struggles, but due to poor judgment and possibly misuse, it spiraled into massive debt  burdening Hae-soo. At some point in the earlier chapters it's insinuated that he took those loans under her name. So he's simply just irresponsible and a jerk

@Oran silvester literally nothing, I think he's used some of the money on those private investigators to track haesoo

@Ashley  *Haesoo

@Oran silvester it's Kang Mincheols debt, when he was married to Hawaii he took out debts under her name that's why she's still stuck paying his debts and works so many part time jobs, also I think that'd the reason they divorced. I think he took other loans after the divorce though