Vexillology

Pretty sure 4 of those are Linux distros.

Top right is the Ubuntu logo. Top green-yellow one is some African country. Bottom one in blue with three triangles is some fancy hotel brand.

It's a shame that they aren't more popular; I didn't really see prefectural flags flown that much outside of government buildings when I lived in Japan.

Third row, second column. Tau Empire.

Top right one looks like a Linux distro logo, so that’s pretty cool I guess

My favorites are probably the flags of Niigata and Okayama. They have really appealing colors imo, and the symbols are great as well (especially Niiagata's).

I don't know which prefecture is attached to the flag but third row, last one to the right, the clover-like one.

Edit; it's the Miyagi prefecture.

These look extremely corporate, like hotel chains.

Bottom left- "et pluribus anus"

Definitely AG Systems

hokkaido!

Far right column, fourth one down from the top. I like that it’s a visual pun on the Japanese flag; the little red dot on a white field inside the larger dot effectively depicts a little Japan inside the larger nation, a microcosm of the nation itself.

It’s a very effective vexillological distinction of a part within a whole, while still maintaining the effect of the original flag design.

I also find it funny that it seems to be a flex on all the other prefectures, this flag subtextually implies, “We’re the most Japanese prefecture that has ever been, we are the essential core of this nation and our absence would leave a blank empty void. Don’t fuck with us.”

6 across, 4 down. The one with the arrows.

I never would have guessed that's what any of these are

Fukuoka for symmetry, Aomori for their flag being a stylised map of Aomori, and Miyagi because it would be fun to draw.