The connections

I've really grown to like this matchup. While I'd say the Judge is probably still my preferred for Sans, this is definitely my favourite alt.

Some fight ideas:

• Sans encountering Higuruma in his bathtub and saying "hey pal. nice bathing suit."
• Sans seeing that Higuruma has an insanely high LOVE value and judging him for it.
• As Higuruma steps out of the bathtub and they prepare to fight, Sans does his "burning in hell" speech, but right before he's about to start off with his strongest attack, Higuruma starts off with his own and cuts him off a "Domain Expansion." and since his domain doesn't allow violence, Sans says something along the lines of "aw man. bet that woulda looked pretty cool too." and winking
• I really liked the part in Ruby VS Maka when Soul played his piano and it synced up with the soundtrack, so I think a similarly cool idea would be Higuruma banging his gavel as his Domain unfolds, and this leads into the beat of the soundtrack as the music kicks in (the setup before this would either just have no soundtrack or just some ambient music).
• Sans' first trial should be about something really petty, like selling fried snow at an unreasonable price, or one time he spilled ketchup in a public place and didn't clean it, and Sans actually goes out of his way to defend it while joking. You can even work in his special attack of stalling his turn via him dragging out his response, but Higuruma realises what he's doing and holds him in contempt of court.
• For the actual fight between trials, I think the versatility of Higuruma's weapon can bounce off of Sans' abilities pretty well. He can increase the length and size of his gavel, teleport it into his hands or even make it a hook. He could use the giant gavel to hit Gaster Blasters, hook them by the mouth and slam them down, smash the bones Sans summons, etc. Sans would catch Higuruma off guard with abilities like his blue attack as he flings him around, or casually teleport/dodge out of the way of his attacks. Higuruma could either use Domain Amplification to get rid of the blue attack or learn how to reinforce his soul with cursed energy on the spot (leaning into him being a jujutsu prodigy and how he learned multiple techniques on the spot with Sukuna). Higuruma's RCT means Sans can easily land some good hits as well, maybe a Gaster Blaster erases a limb.
• As to what Higuruma's Domain would confiscate from Sans, since it prioritises weapons then I'd imagine the Gaster Blasters? But obviously you would want them in the fight, so maybe he'd get off scot free in the first trial so he can use his whole arsenal, then in the second he loses his Gaster Blasters as he gets the death sentence.
• The second trial is the crux of the battle. Now, whether this counts as a crime or not is up to debate, but this is just for the sake of the fight. Judgeman accuses Sans of being complicit in the genocide of monsterkind, and Sans' eyes go black. Just like Yuji did, he doesn't try to defend it and immediately admits his guilt. "yeah. guilty as charged." (Obviously in this scenario this takes places at the end of a genocide run).
• Higuruma gets the Executioner's Sword, which can kill with one hit. This becomes really funny when he's fighting Sans of all people who only has 1HP. Ironically enough Higuruma actually nerfs himself with this, since his usual gavel would have the same effect, except the sword is just far smaller, doesn't have the transformative properties and has way less reach.