Beware of spoilers!
This event is called “Head-over-heels!” (ゾッコン！/zokkon!)
This event is similar to one of Rod’s in A New Beginning, replacing Rod with Fritz and Allen with Reager. Fritz is much more energetic than Rod, though! (Which is kind of scary, really, considering that Rod too is a very energetic young man…) And poor Reager… He doesn’t like putting up with other couples’ displays of affection, as is also demonstrated in Mistel’s yellow event.
The event is triggered by going to the 2nd floor of the restaurant on a Wednesday evening/night. You must make sure to go up to the 2nd floor! Merely entering the restaurant won’t trigger the event.
I’m not entirely sure if Reega’s English name is spelled as “Reager” or “Raeger” because I have seen both given as the official name. I’m sticking with “Reager” for now.