This is always there, though.
This space in the store always has this for some series. In March, they had Idolish 7, and in between, they had... I want to say it was Laid Back Camp, but I don't entirely remember. Last February, they had a display of costumes from the Tsukiuta stage play. Currently, this store also has costumes from the Acca stage play on display.
A few blocks away, in the Marui department store that has the permanent Production I.G. and One Piece stores, there's a Broccoli otome game pop up shop that has similar displays, including costumes from the Kamigami no Asobi stage play. There are also plenty of other spaces like this in Tokyo, especially in Akihabara and Ikebukuro, not to mention probably some in Osaka and other places too. (Voice actors' hometowns' anime shops often have special events and displays for their work, for instance).
The Marui in Shinjuku with the permanent Godzilla store and Animate cafe also has a Digimon pop-up on the ground floor currently, with a Code Geass one coming after that - Gakuen Babysitters was before Digimon - and AkaSeka, Love Live, and other pop-ups on higher floors.
Those star post-it boards, where fans can write messages for the series, are always there, especially for characters' birthdays. This Animate's Tsukiuta aisle always has one for the month's representatives, as well as displays like standees, and, in March, they covered the aisle with pictures of Haru's glasses. A crane arcade in Ikebukuro used to have that for Durarara characters, too, for obvious reasons.
And that's not counting cafes, karaoke collabs, and other special in-person events that aren't any different from this. I realize you can't cover every single pop-up in Japan, but just covering the ones for popular series doesn't seem fair. Maybe a bi-weekly or monthly roundup with be better?