Sushi: uncooked damage turning into advantage
The build wants to take advantage of Kaito and his delightful ninjutsu mechanic, which not only fields a crazy-strong walker/critter that's a win condition all on its own, but also allows you to bounce your own critter for advantage.
Thus, Kaito advantage + critter advantage + relative tempo = inevitability bonanza converted into a win.
Bouncing your own critters is either directly or indirectly helpful in the build as follows: Borrower's flash, bounce, and, flying make it ideal for Kaito, as you can cast it early as temp-removal/permanent removal (tokens, etc), then flash it in in an endstep and swing with flying next turn, which probably won't get blocked. You can even use its bounce abil to bounce any potential blockers, flash it in, then bounce it to Kaito since there are no available blockers. Then you get to reuse it all over again. Bowmasters basically speaks for itself. Its ETB gives you damage and material at speed, and reusing it through a Kaito bounce does nothing but help the build go over the top. Snapcaster has endless targets, flashes in, can remove blockers, it's just delightful to synergize with Kaito. Tamiyo is obviously good on its own, but finds a special place in a Kaito build. 0/3 flyer has almost no chance of dying to blocks in modern (beyond a smelly old Murktide), so you can use it to get Kaito in very reliably. Since you attacked with it, even if you Kaito bounce it, you get the Clue token on top for extra advantage. It's also so cheap that you can usually recast it in the same turn, which lets you potentially transform it either that turn or the next turn, as Kaito gives you draw number 2 and a Clue hits for draw number 3. So 6 mana flips Tamiyo in a turn, or 2-3 mana flips Tamiyo on the next turn (if all goes well). Any way you slice it, turn 1 or 2 Tamiyo waiting for a Kaito turn 3 or 4 is a great way to open a game.
Kaito is also cheap enough on his own that he makes for a great topdeck, even if you can't ninjutsu him in. There's really nothing to dislike about the card. He comes in on 4, so he's not boltable. He builds to his own win condition, has critter control if you need it, and has card advantage if you need it while having a consistent potential damage clock. Unlike most other win conditions, he doesn't actually require any other cards or conditions, and is perfectly fine paying his regular cost instead of his alternate cost (if necessary). Obviously you'd rather get the bounce advantage, but if that's not available, your deck is still doing what it's supposed to do just by casting him and going to work.
And, perhaps best of all, the deck essentially doesn't care about your grave, beyond Snap, unlike so many Dimir decks in modern. So opponent has a good chance of siding in grave hate that's essentially completely useless.
Thoughts appreciated.