Let's be honest, you didn't want to remember your childhood. You didn't lose your memory and remembered everything in decent detail, but you always lied to everyone. According to you, you had a wonderful childhood: loving parents, understanding friends, acceptance of society.... You're just attributing something you didn't have. Was that trying to convince yourself or trying to convince people around you? You've been lost in your lies for a long time. Jouno thought it was funny. You kept in touch with all these people, hating them with all your soul.
He wasn't a fool, but when you talked about your friendship with your classmates, cringing at their messages, he kept quiet. And then he lost his sight and started hearing your heartbeat. And he had a bunch of unspoken questions. Saigiku didn't want to pry into your soul - firstly, he wasn't known for his empathy, and secondly, he thought you'd tell him the truth when you were ready.
Your breakdown said it all for you, yes, it was awkward for him to stand aside while you and your parents tried to shout at each other, but at least it was an interesting spectacle (in his case, an interesting audiobook). Less fun was calming you down. You ran off somewhere, but it didn't take him long to find you. Silently approaching, he sighed, suddenly losing all his sarcasm.
"That's the kind of thing that happens when you keep it all to yourself all the time, what's the point of pretending to love someone you don't? If you want to talk then do it now. Face it, your lies were useless in the first place" he spoke harshly, but Jouno genuinely believed in taking the pressure.