They probably wrote it off "because she's family", you definitely see that dynamic sometimes where people don't feel like they have the right to intrude on interactions between family even if they're crossing some lines. Naturally Tetsu intruded because he feels like he has the right to (or doesn't care, I guess)

My read on that is honestly closer to: Ten was overly excited by Mogu's sister just existing inside the cafe, if he saw at all. The way the panels are framed we can't see the rest of the restaurant, but it's also not unreasonable to think that Ten might have been otherwise occupied, and just heard the outburst rather than saw it.
Mei: Clearly sees something is wrong via Mogu's expression and demeanor, but hasn't yet had time to follow it up.
The others just weren't present.
As for Tetsu, he's their boyfriend! He's seeing his significant other in significant distress, and acting quite out of character, and has just born witness to one of Sakura's outbursts. However, he's coming from a position of little to no information, so until Mogu chooses to talk to him about it, all he can really do is be as caring and supportive as he really can. But he's not going to just let anyone shout and tear down Mogu, especially in the middle of his cafe.

last edited at May 3, 2020 12:10PM