 If you liked
Kimi ga Bokura wo Akuma to Yonda Koro
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 ...then you might like
Pigpen
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Both mangas explore the topic of guilt after commiting a horrible crime, that of course can not simply be forgiven. Main characters I wouldn't say are simmilar, but it is had to be said that there are aspects which they share, especially at the end.
Also one of the most important details is the amnesia aspect, not only the fact that main character has amnesia, but how story progresses and how main character remembers fragments of his past.