Lord El-Melloi II’s Case Files {Rail Zeppelin} Grace note -Special Episode- is a special anime that premiered in fall 2021, produced by TROYCA.

About the production: the story comes from a light novel, there is 1 episode of about 53 minutes and its current status is "finished".

Its main genres are drama, fantasy and mystery, with themes such as Magic, Age Regression, Photography and Curses.

On AniList, Lord El-Melloi II’s Case Files {Rail Zeppelin} Grace note -Special Episode- has an average score of 74%, a good score, and appears on 14,730 users' lists.

The franchise continues in or follows from: Lord El-Melloi II-sei no Jikenbo: "Rail Zeppelin" Grace note.

A letter is delivered to Lord El-Melloi II informing him of a Clock Tower reunion. One morning, as the reunion's date draws near, Lord El-Melloi II takes a look in the mirror and reels in shock. He is suddenly a full decade younger! Lord El-Melloi II has become Waver Velvet, his former self! Believing himself to be in the grip of a powerful, magically induced delusion, Lord El-Melloi II immediately begins investigating how this could have happened. On the day of the reunion, he makes his way to the gathering of his contemporaries, planning to confront whoever transformed his body and hoping to reveal their intentions. However, when Touko Aozaki arrives, things take a sudden turn... (Source: Crunchyroll) Note: The special edition was broadcasted in the Fate Project New Year's Eve TV Special 2021.

Official synopsis from AniList.