It's literally just stupid at this point. This entire manga is an example of "How framing makes a story".
Cut out the middle panel on page 3 of this guy hesitating to answer with a pounding heart and you know what you have?
LITERALLY NOTHING HAPPENING
Girl asks her stepdad a question, he is confused, she leaves the room. End of chapter.
90% of what makes this series "psychological" is the tags on the website and the odd framing panel that makes things more suggestive than they'd otherwise be.
Someone else could write this entire story changing none of the dialogue, and it could be a gentle drama series about a new family trying to settle in together. (Skipping chapter 10 of course)