(add Change Plans, Contractual Safeguard, Cryptic Pursuit, Damning Verdict, False Door)

There are a couple of cards I want to justify as being "essential", that being Drift of Phantasms and Search for Glory.  They are limited in what they can search for, but importantly they can find you Feather, the Redeemed, which is a key card to this deck taking over a game.  There are about 10-15 cards deemed essential that can mass-target, including "harmlessly" targeting one of our own crits, allowing Feather to bring the spell back to hand at the end of the turn and reuse it again when necessary.  That means potentially casting the same spell on each person's turn, assuming you have the mana to do it (and Hinata makes that more realistic).  There aren't too many other ways to search for Feather (Thalia's Lancers and Nahiri, the Harbinger?), so these are a few of the best options available.  That being said, if Feather is already in hand/play, there are lots of worthy 3cc cards, or legendary cards (or sagas...?) for us to tutor for.  As mentioned below, Sublime Epiphany and Mystic Confluence are two counter spells that can each be cast for two blue mana, and target a creature you control to allow Feather to return it to your hand at the end of the turn.  S.Epiphany is a hard counter, and M.Confluence can force an opponent to pay 3 or 6 mana to keep casting their spell, which is a hard counter most of the time.

Many of the cards I think are essential to Hinata hinge on the concept that you will be making him and/or other creatures unblockable in combat, usually by tapping all your opponent's creatures.  This also hinges on being able to reuse these spells to repeat this effect, ideally with Feather, the Redeemed.

Parallel Thoughts is a fun card in this deck, because it's easy to populate the exiled seven cards with instant and sorcry spells we can cast for cheap, and ideally we'll have plenty of mass-draw options in the deck that will allow us to draw those seven cards before Parallel Thoughts gets removed.  While I like lots of draw cards in my decks, the following list contains more than anyone needs, and many are inexpensive to purchase.  So far my research has found these cards to jive the best with Hinata (or they're just be too powerful not to include), as well as having many unblockable creatures, which I think makes sense in a deck where Hinata can have access to tapping opponent's creatures so easily/often, so in no particular order: Righteous Authority, Consecrated Sphinx, Esper Sentinel, Surrakar Spellblade, Mystic Remora, Open Into Wonder, Paradoxical Outcome, Rhystic Study,Sea Gate Restoration, The Magic Mirror, Verity Circle, Bident of Thassa, Coastal Piracy, Deepfathom Skulker, and Reconnaissance Mission.

Crackle with Power... with Hinata's cost reductions, if X = 4, you pay 10 mana to deal 20 damage to each of four targets/players, or 12 mana to deal 25 damage to each of five targets/players... just saying.  Also, it doesn't exile itself, so you can theoretically find a way to cast it again.  Great spell to copy too.

Sublime Epiphany and Mystic Confluence is pretty fun with Feather, the Redeemed in play, and with Hinata.  Assuming you have creature tokens or a cheap-to-cast creature in play to bounce to your hand, you can keep returning Mystic confluence to your hand after countering spells.  Target the spell you want to counter twice, then target a creature you control to bounce to your hand, and only pay two blue mana.  Or counter the spell once and also return a creature to an opponent's hand.  Or counter the spell, bounce a crit to your hand, and draw a card instead, and pay 3cc total.  Sublime Epiphany can do the same, but by targeting your own creature to copy, you qualify it for Feather's return to hand ability, eliminating the need to bounce a creature to your hand.  Sublime Epiphany is nutsy powerful in a Hinata deck, and being able to reuse it every turn is just laughable... so long as it's used primarily as a counterspell, it'll usually be very easy to reduce it by 4cc and only play two blue mana... HARD counter a spell, bounce a permanent to an opponent's hand, copy a (nonlegendary) creature you control, and draw a card... every turn you can afford the two blue mana and want to counter a spell.  Oy....

Kaho, Minamo Historian is an intriguing piece to add, as he adds access to whatever we feel is important at the moment, with the caveat that he and thosecards could disappear before getting to use them if we can't get him haste (Lightning Greaves, etc).  It would be understandable to tuck some counterspells into Kaho's pocket, like Disallow or Sublime Epiphany, maybe a protection spell like Teferi's Protection or Disorder in the Court, and/or something with some serious board control, like a Cyclonic Rift or Heliod's Intervention, or simple targeted removal with Generous Gift.  Kudos if you can flicker Kaho and recharge his cache of spells.  Also, remember that he has to ETB before you search for the spells, so opponents have to decide to counter him prior to finding out what you're grabbing... this means there is an opoortunity to make deals and play some politics... I remove this if you do that, etc.

Lithoform Engine is great for copying your spells and effects, but in a control deck stocked with counterspells, don't forget that if someone tries to counter your counterspell you can use this to copy your counterspell again too.  Of if someone wants to counter one of your mass instant/sorcery spells, this lets you copy your spell and continue on.  Hard to understand why this card isn't worth more.  It will be eventually.

Firemind's Foresight is fun if it doesn't get countered.  Hmmm.... March of Swirling Mist or Mystical Tutor (1), Cyclonic Rift, Heliod's Intervention or Mana Drain (2), and Disallow or Generous Gift (3)...?  Yeah, 7cc is spendy, but the mid/late game value this gives you is pretty creazy.

Because some instant spells can copy any other instant, they turn into counterspells of counterspells.  Obviously they can also double-up a big spell you have too, but in a Hinata deck, if you're going to include spells that copy your spells, IMHO they should either be able to copy any player's instant/sorcery, or they should be able to copy a spell more than once.  Anything else is a downgrade.  And I would only include them if you are leaning heavier on damage spells you would intend to copy.