This deck is built for high-power casual/optimized play. This is not meant for competitive EDH, nor is it meant for lower powered casual play.
The deck's goal is to get Yuriko out on turn 2, hence the glut of 1 drops. I don't like 2 drops as it is very expensive to cast -> ninjutsu -> recast (total of 6 mana if using Yuriko) whereas a 1 drop will only cost 4 mana to do the same. Ninjutsu is a very tempo-negative ability so it's best if your creatures cost as little as possible.
In terms of the 0-1 mana cost ones, I only included ones that are evasive and/or have some kind of additional bonus. With 14 0-1 mana cost creatures, I have about a 96% chance of drawing at least one in my first 3 opening hands. The easiest way to recover from mulling is to have 2 lands and a 1 drop in the opener, and I've won so many games mulling to 5 or even 4 because of that.
Extra turn cards are mainly used as extra combats, and you always want to see them.
Here are some cards I don't have money for, but would suggest if you're looking to upgrade:
Underground Sea (cut Sunken Hollow)
Capture of Jingzhou (cut Walk the Aeons)
Notable cuts:
Commit / Memory - great card, expensive effect. Cut for Dig Through Time which has actual utility.
Preordain, Ponder - Worse than the other 1 cmc top of library setup cards such as Brainstorm, Vampiric Tutor, Mystical Tutor, and Scheming Symmetry.
Thalakos Seer, Baleful Strix and other 2 cmc ninjutsu enablers in general - as stated earlier, 1 drops are king. I find I don't need the extra draw from these guys and I'd rather just have more 1 drops.
Drowned Catacomb - not great in this deck because it only has a 67% chance of coming in untapped (assuming i slot it in over another nonbasic) on turn 2, which is my crucial turn. River of Tears and basic Swamp are both better. Sunken Hollow gets the nod over it because it's another fetchable blue source off a black fetchland.
Dimir Signet - kind of awkward since this deck hates black mana and has a bunch of 1 cmc spells, was cut for Mox Diamond which I recently acquired. There were a lot of games where being forced to filter UU into UB just to get another mana hurt me.
Talisman of Dominance - Had this for a long time, and it's way better than Dimir Signet, but at the end of the day I realized that this deck doesn't really want to be paying 2 for a ramp spell.
Unnatural Selection, Standardize - just kinda clunky.
Conspiracy, Xenograft - 5 mana is a lot. Also I've gone down on 1 drops due to London mulligan, making these cards worse.
Toxic Deluge - a sweet card, but I never found myself wanting to tutor for it or cast it.
Cunning Evasion - card didn't end up panning out, you often have to wait a turn before it's effective. It's often just better to play something that will clear a blocker for a turn.
Sakashima the Impostor - too easy to get blown out when trying to copy Yuriko. I hate tapping out precombat.
Diabolic Intent - very tempo negative play and the deck typically doesn't need to tutor often.
Due to Modern Horizons, there are now lots and lots of Ninjas, and because the list is so tight there are a bunch that didn't make it in! Sorry to the following Ninjas who are just not good enough to make it in:
Azra Smokeshaper - weak abilities
Higure, the Still Wind - The most recently cut Ninja since I acquired an Imperial Seal. 4 mana is a lot to ask for ninjutsu, and unlike Fallen Shinobi his "on damage" ability is largely irrelevant. I've also rarely had enough mana to activate his unblockable ability, and so sadly he got cut.
Ink-Eyes, Servant of Oni - I really didn't want to cut this as it's my favorite creature, but it makes me sad that I never have the mana to ninja her out, or if I do, there are better things I could be doing. There are also many times where her ability just doesn't matter at all. Most times I just ended up discarding her to max hand size or Insidious Dreams, and my bae doesn't deserve that.
Moonblade Shinobi - has been in and out of the deck; the card is comparable to Throat Slitter and I value the removal a little more than the the extra enablers.
Ninja of the New Moon - uh... no.
Okiba-Gang Shinobi - recently cut for being expensive for its effect.
Silent-Blade Oni - recently cut with the advent of all the new ninjas. 6 mana is a lot to ask regardless of how strong the effect is, and sometimes the ability doesn't even do much.
Phantom Ninja - another card that just barely misses the mark. I would actually really like to try this card out, but it just seems so bad. At 3 mana, I'd rather Ninjutsu something so it attacks right away.
Throatseeker - don't care much about lifelink. worse than Phantom Ninja who didn't make it in.
