Len'en Reiretsuden~ Reactivate Majestical Imperial (??????? Reactivate majestical imperial) is a vertical-scrolling danmaku shoot 'em up and the third game of the Len'en Project. It was made by Trick Nostalgie's sole member JynX and released for the Windows operating system. The first trial version of the game was sold at Winter Comiket 2013, and the updated public trial version was released on 19 March 2014. The full version of the game was released on 2 October 2014 as a free download.

ike previous Len'en Project games, the title consist mainly of five Japanese kanji, plus an English sub-title that relates to the main title without necessarily being a translation. In the title, "Reiretsuden (???)" is referencing the amount of spirits that are coming to Mugenri in the game's plot. "Reactivate Majestical Imperial" refers to the resurrection ceremony of Taira no Masakado, a ritual held by Taira no Fumikado to become the new emperor of the capital. The Japanese title was originally "?????", but it was changed to "?????" in v1.10 in accordance with Brilliant Pagoda or Haze Castle. Unlike previous games, "Reactivate Majestical Imperial" is officially written in lower-case.