Spring Equinox (Ostara) (March 20th or 21st)
This is a public holiday in Japan (called Shunbun no Hi) and is the midpoint of the period known as Higan – a time for remembering the ancestors. You can read more about the Spring Equinox in Japan here. You are unlikely to find many Easter/Ostara-themed goods like eggs outside of specialist import stores (Japan doesn’t celebrate Easter), but you will find lots of other spring-related things for your altar – consider taking inspiration from Hina Matsuri (Girl’s Day) decorations (read more about Hina Matsuri here).