It’s Denkigai. It’s in Belle Salle Shinjuku Grand, where it was also held few years ago. It’s a nice place though mostly just for nostalgic reason.
I didn’t intend to buy anything there and just passing by before going to POP Fes. And ended up not buying anything except for a friend. Also got a chance to take a quick look at the booklet. Maybe I should buy it for once at next event. If they’re doing it again next year, that is.