Silent Möbius gaiden: Bakumatsu Anbu shimatsu ki

Despite being older than the series (just like both anime movies), this might be covering the missing ending of the anime series, i. e. the events of manga chapter 12; the VHS tape is still available in Japan. Amongst the staff are Nami and Yuki, as well as Katsumi with a different family name (Katsumi Himi), with the same seiyuu as in the anime series. (Wikipedia)