The premise (trauma->rehabilitation->redemption) was interesting. The setting/context, while controversial (teacher-student relationship with a big age gap), was also an interesting complement to the premise. Ultimately, the series gets ruined by several pretty much dogshit approaches:
1) Pacing. Holy hell, this series went into the weirdest pacing overdrive in its last 10ish chapters or so. It felt borderline like a fever dream (in the bad sense of things), jumping erratically from plot line to plot line, from random minor character/situation to another random minor character/situation.
Barely comprehensible, and this terrible pacing was further amplified by...
2) The weird jumping from serious/dark/emotional moments to weird comedy. You can have both of these under the roof of a series, but the constant switch between moods in absolutely inappropriate situations made me cringe. I won't mention specific chapters where this was exceptionally bad so as not to spoil readers.
However, at times it's absurd. With the bad pacing complementing this, some plot points were barely readable and I was at a loss on how to react to what's happening.
3) Absolutely bland and boring side characters. I get it, it's a short manga, but I've seen many short series do side characters justice. Not here. Every single one of them is as 1D as it gets, and they pop up in the weirdest of moments quite often, just to get discarded in a rash way. We were better off without most of them and fleshing out the MC/FMC interactions more or digging deeper into the trauma/redemption psychology aspects.
4) Plot devices. Using rape as a plot device once? Er, alright...it's a cliche, but can still work. Using it several times? Yeah, that pretty much shows you have no idea how to drive conflict and approach resolution.
'Midara na Kimi ni Kamaretai' gets a 5/10 from me, with 2 of these points being given just for the otherwise interesting premise that could have been explored. The setting was perfect for a more psychological, darker, trauma->healing-focused manga. It failed to approach the subject well. A few more points for some genuinely cute moments (if we glance over the age gap involved) and some decent more steamy scenes, but that's just about it.
