I’m not even sure if it’s fine to post this video… It’s taken from the official Reitaisai streaming, btw.

Anyway: the “Reitaisai Collab Unit Song” (temporary name) has been revealed! It’s basically a big medley of famous Touhou themes and each circle is in charge of a certain portion:
– Maiden’s Capriccio (intro)
– U.N. Owen Was Her? [Kishida Kyoudan]
– Necrofantasia [BUTAOTOME]
– Reach for the Moon, Immortal Smoke [Yuuhei Satellite]
– Eastern Judgement in the Sixtieth Year ~ Fate of Sixty Years [Alstroemeria Records]
– Love-Colored Master Spark [COOL&CREATE]
– Native Faith [A-One]
– Theme of Eastern Story (everybody’s chorus)

If I understood correctly, the complete edition will feature a public recording of the chorus sung by people attending Reitaisai

EDIT: the livestream video has been removed, but the song has been officially uploaded on Niconico! Link