Episode: Bakumatsu: Ren`ai Bakumatsu Kareshi Gaiden - Crisis - 12 - To a New Bakumatsu!

"You're not going anywhere!!" Having become one with the giant castle Susanoo, the hulking figure of the castle and Mugensai stalks towards Lake Ogura to make his plan to plunge Japan into a world of unending war a reality. However, Takasugi, Katsura, Yoshinobu, and the Shinsengumi stand in his way and put their lives on the line to prevent his plan from taking fruit. The longstanding conflict that Takasugi and his companions have been struggling to deal with finally seems to be near its end! How will their feelings surrounding the chronometer be resolved? And what new age will be awaiting them when this is all finished?

Source: crunchyroll