He can't help it since Hae-In's Dad is begging on his knees to Doo-Joon and as his former student, instead of jail he sent her to medical institution out of pity for the Dad
But he can help it. He just feels a sense of gratitude and respect for him which I get but this is bigger than him at this point. It’d be a different thing if it was just him being affected by Hae-In’s actions but now he’s affecting his wife and unborn child and by extension that can affect her friends and family. This has everything to do with Heewons safety and nothing to do with Doo-Joons teachers crazy ass daughter. Heewon needs to be his priority.
Yeah, yes indeed but a father can't bear to see his child rot behind the cell thats why Doo Joon can't put her to a cell. But there's also a way though, not in the medical institution, but instead send her far away that no one knows else where and begin a new life, though must be kept on security just incase it'll turn crazy in any point but that is also one of the best options aside to put her behind the cell
Heewon is starting to get paranoid. This could all be avoided if Doo-Joon just puts that pinkie pie bitch in jail where she belongs. But alas he won’t understand until something happens to Heewon unfortunately. UHHH GODDAMMIT DOO-JOON.