Type-Moon hired Tsukumo, the artist who previously drew doujins of the Fate characters watching the series and playing Fate/Grand Order to draw official comics promoting the Heaven's Feel movies. The first comic was published on the official movie website for the release of the second Heaven's Feel movie and the second comic was published for the release of the third movie.

Source: https://www.fate-sn.com/2nd/special/manga/