In episode 9 of The Boyfriend, titled Accepting You No Matter What, Shun is upset with Dai, who doesn't know why. Dai later realizes it might be because he wore a different T-shirt instead of Shun's suggestion. The episode also shows fellow housemates Kazuto, Alan, and Ikuo worried about Dai due to Shun's different behavior.
Later in the episode, Ikuo was also seen sharing his worries with Dai regarding Shun. The cast member was seen saying—
"When I see you, it’s really painful for me."
The official synopsis for The Boyfriend episode 9 reads—
"Dai confides in a few members for advice. Ikuo’s good intentions backfire. As things cool down, a surprise announcement leaves the boys in tears."
The Boyfriend episode 9: What happened between Dai and Shun’s relationship?
After Gensei was announced as the shift in charge for that day, he chose Ryota to go with him on the work shift. Later when all the housemates were discussing things to be done that day, Shun didn’t seem interested.
He asked—
"Can I be by myself?"
Alan asked what happened. Shun shared that—
"Right now, I can’t enjoy myself around somebody. That’s why I need a little space."
Kazuto asked whether Shun needed space from the rest of the housemates or anyone in particular. Shun said, (pointing to) Dai, “From him.”
Everyone wondered what went wrong between Shun and Dai, which even the latter had no idea about. Alan asked if he wanted to share why he was upset. Shun answered, “It’s a hassle.” They also asked Dai if he wanted to share anything. But he also refused, as he didn’t know why Shun was upset. Shun then walked out, and everyone else continued the conversation.
Dai then remembered something that had happened the day before and shared with the group—
"One thing comes to my mind. Yesterday, before I took a bath, Shun said, “You can wear this T-shirt, it’s clean. I just wore it for a little while. I said, “Thanks. I’m good. I have a new one.” But he insisted, “Hey this one’s clean.” So I took at the time saying, “Oh, okay.” "
He continued—
"But then I just put on what I wanted to wear just like I usually do. So yeah, I put on my T-shirt and I went upstairs to get a face mask, and Shut said, “You’re not wearing that."
Kazuto agreed and said, “That’s definitely it.”
Ikuo and Dai’s conversation: The Boyfriend episode 9
Dai and Ikuo went outside to talk. Ikuo expressed his concern for Dai, saying it pains him to see Dai being so patient with Shun, despite Shun's difficult behavior.
However, Dai felt otherwise, as he told Ikuo—
"I’m not gonna give up on him until I’m worn out. I don’t know who’ll get worn out first, though."
Fans can stream The Boyfriend on Netflix.