Fukushuu no Taishi - Level 9999 no Bakumatsu Isekai Tensei is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

During the end of the Edo Period, the Shinsengumi are suddenly transferred to another world. As they arrive, a guide from the other world, Hangya, appears and tells them, “There’s only one way for you all to return to your former world. Please, defeat the Demon Lord.” This is a tale of the weakest warriors becoming the strongest.