im going to copy what my friend said abt this question since im bad at explaining things

Haruka views Muu as his mother, and whilst his idea of a mother is twisted and not an example of an actual mother, it’s actually worse that he envisions her in such a way due to the fact that his ACTUAL mother was horrible, abusive and manipulative. Also, Haruka has a weird deep obsession with his mother which is unhealthy, and to project that onto someone else, especially a teenage girl, is weird and gross. Toxic ships exist yes, but this one borders on being gross due to the ‘ mother son ‘ dynamic presented ( especially due to it being a twisted dynamic at that ) as well as the fact a lot of people embrace/ship it DUE to this weird dynamic at play ( and sometimes even use mommy kinks as an example of it being okay despite the people in question being minors ) and not only that, the ship itself can be categorised as pseudo-incestuous due to the fact Haruka, again, sees Muu as a maternal figure in canon ) Not to mention the ship itself, by existing, minimalises Haruka’s trauma as a “ romantic “ thing when it is actually a very bad and very wrong trauma response.