I thought he would try and conceal it, but it looks like he is willing to tell her (if she didn't know already, that is). According to the description this manga is about "guilt & atonement" - but there are multiple ways of atoning for one's actions. Will this go the retribution route, or the forgiveness route moving forward? (Looking at chapter 1, page 3 hopefully it is forgiveness.)
No one that has been introduced in the story so far has gotten off lightly. One person can cause so much hurt, and damage.