Kichijitsu Goyomi by Iwaoka Hisae, running in Feel Young, is basically a wedding planner Competence Porn manga. The current couple in chapter 9, to be continued in 10, is 2 women. While they can't legally marry yet, same sex couples do hold wedding ceremonies in Japan. The chapter was about stuff like how the couple met, started their relationship and came out to their parents, but also partly about the extra friction they experience from wedding venues, but the protagonist will presumably get them the garden wedding they want.
MangaPlaza seems to have the series as Days Full of Promise, up to chapter 5 (i.e., volume 1).