those groups are part of a group of groups. they are like sister groups , they share same pool of artists. there is 3 other groups but they are not as active as mimizu and ichi. they are consisting of artists that used to make art for softhouse seal/soft hous seal grandee and their brand of games in the past. however since softhouse seal stop making games and bacame cryptoseal a group that focus on their yome crypto systems "characters from their games are (yome) and people sell and trade cards of said characters and establish value of the yome" the artists decided to make doujin cg sets , hence why there is more than one group that release stuff around the same time.
Base +4, Thanks +7, Rephikul +8, Prasadidasi +7, SirIndigo +11