Miacis is a genus of extinct carnivorous mammals believed to be the ancestors of dogs and cats.
As for the second word of the title, according to Kato-san, as the stories of all the characters - each of the 'Miacis' - interweave, they create a whole symphony.
The chapter starts off with, "I screwed up".
We meet a man in his 40s who is taking his daughter, Marina (she just turned 20), out for a meal in a Japanese-style restaurant for the first time in 10 years - actually, they haven't even seen each other in person for 2 years. The girl's mother supposedly doesn't have a good opinion on her daughter's father (also we get to know she doesn't approve of Marina drinking alcohol - the girl decides to drink soda with plum wine anyway). The man is nervous, hangover and desperately needs to use the bathroom, but doesn't want to seem uncool. Things are very awkward, and the owner of the place (taisho) making jokes doesn't help at all. However, thanks to him we find out the main character’s name - Tacchan.
At some point Tacchan can't hold it anymore and heads to the toilet - a facility only meant for one person per time at this restaurant, and someone who's already inside is taking forever to do their business. The man shuffles and stomps and coughs deliberately, then knocks on the door as the last resort. The door opens, and he sees a beautiful woman, who, passing him silently at first, then suddenly turns around and says with a stern expression, "Excuse me. Did I really take that long?" Tacchan blurts out a confused "I'm sorry" and flees to the bathroom.
Almost immediately though he gets indignant thinking that the woman should've apologized instead, even if just out of politeness. He makes sure to finish his business in record time, as if to prove a point to the woman of how quick one should be in situations like this. When Marina asks him if he's alright, noting in an embarrassed tone that he took quite a while in the bathroom, he can't help exclaiming, "It was a long time, right?!"
Marina orders that soda with plum wine, and he says, "It's okay to get tipsy, I'll take you home properly" - thinking that he can finally act like a father. Marina replies with, "Normally, a father would say not to drink too much". The poor man feels the need to use the bathroom again.
The main female character, Yuu, is having a crisis over her friend (?), Misa, being in a different restaurant with Yuu's never-made-it-official boyfriend Ryouta at that very moment. Misa left her a LINE message saying that Ryouta, ostensibly, wanted to talk about Yuu and she thought of declining first, then decided it was only a meal, and she doesn't want to make Yuu uncomfortable but couldn't conceal it either etc, etc. Yuu replies with "It's fine, we broke up anyway". She recalls a similar occasion from the past: working her butt off part-time to buy silver earrings, and Misa buying them first with her parents' money. What we get to know about Ryouta is that he loves desserts (unlike Yuu herself, but she found that cute) and playing around.
So, Yuu is in turmoil while she's supposed to be having a meal with a person named Aoi, whom she'd agreed to meet on her brother-in-law's insistence (the guy's too stiff, and "spending some time around women might do him good"). She ends up taking her anger out on our Mess-of-a-Dad, regrets it but also finds his facial expression extremely comical.
As Aoi-san finally arrives (he texted her apologizing for being late), unimpressive and trying too hard to be pleasant, she can see right away that he isn't her type at all. When Aoi asks Yuu what made her smile on her way back from the bathroom (she was actually expecting to hear the phrase "You looked like you had been crying"), she goes, "To hell with it" and just tells him everything - about Ryouta, Misa and the guy on the other side of the bathroom door. "His face looked like a crumpled tissue!"
"What was it like, could you show me?" The stiff Aoi-san's sudden interest in her boring story takes Yuu by surprise. Even after oversharing like that she's too embarrassed to do an actual impersonation, and then Aoi himself starts making horrible, hilarious faces. Laughing, she says, "No, like this!" and does an impersonation of the Toilet Guy.
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A big thank you to
mckee16_88 who kindly shared the scans of this series with me