A temple or alter built to honor your waifu/husbando, often in a closet. It is a hole in the wall where you can worship your oshi.
I stuffed my bodypillows of Aia Amare and Scarle Yonaguni, from Nijisanji EN, right into my oshi hole. Its a snug fit, but I can finally do my daily prayers while enveloped in their divine presence.