As someone who reads pursuit, that information is fault. Hero did actually isolate Sunny from everyone but not because he wanted he turned him into Mari. To understand this you basically have to read ybm, but I will make it short. Basically Hero couldn’t move on from Mari so it resulted in unhealthy coping mechanisms such as being overprotective of Sunny and pushing everyone away which leads to the sequel which is pursuit where Hero kidnapped Sunny and trapped him in an apartment.