The Cycle of Cards Game

{You Killed My Father/ZephyrPhantom }
Card Balance ★★★★★ ( ☆☆☆★★ )
The critical point is that this is a sorcery.
In many cases, it can kill nothing.
I guess that my mention was wrong worded and you didn't notice this problem and you really intended was an instant with same ability.
If so, I feel kind of it might be black rather than white because the restriction is very similar to "sacrifice a creature or pay life equal to target's power".
I feel that this kind of "retribution of justice" got not to be a white mechanic though this flavor is still belonging to white.
But maybe this is only a passing tendency. I don't think this mechanic is far from white's essential role.
As a sorcery, I estimate it is the worst but if it is an instant, it is almost nicely balanced.

Flavor ☆☆★★★ ( ☆☆☆☆☆ )
If it is an instant, the flavor is attractive.
Rage for revenge enables you to defeat your enemy regardless of how it is strong.
If it is a sorcery, I feel the one who is represented by this spell would be very calm person and rarely get angry. But I wonder why he gets so angry only at blockers who activated its tapping ability to pump or so during the combat.

How Famous the Phrase Is ☆☆☆☆★
The Princess Bride is not so famous in Japan. Even its title is not well-known.
Star Wars is very popular in Japan too. The popularity is far superior to Fist of the North Star.
The phrase "You Killed My Father" itself is not so famous but Darth's response, I Am Your Father, is enough famous though not so much as the North Star. The manga is not so popular but the phrase's famousness is tremendous.

Fitness with Kamigawa ☆☆☆★★
The flavor text is fit with Kamigawa. Has a taste of samurai.

Role in Limited ★★★★★ ( ☆☆★★★ )
Even if it is an instant, it doesn't fit with any of NEO archetypes.
Sometimes it maybe used in a white defensive deck which lacks creature removal.

{Momantai/Flo00 }
Card Balance ☆☆☆☆★
Interesting card.
Since it is not "up to one target", it is hard to be used in a control deck with a few creatures. But it would be a good stuff for most decks in limited.
White beatdown in standard might adopt it. Though it gives your opponent 3 life but StP was used even though its drawback.
I feel the correspondence between this card and StP is similar with Counterspell and Remand.
Cyclable for 1 mana, helps you to survive the lethal attack, temporary remove of blocker to deal 4 or more damage etc, it has a various usage.
The reason why I didn't give it 5 point is that you can cast it to your creature to gain 3 life and draw a card. Though you have a risk to fizzle if you do so, it is too stronger than Revitalize.

Flavor ☆☆☆☆★
Expressing the state of stuffed with tapping and life is unique.
Also I like it gives 3 life, which is equal to Food's life.

How Famous the Phrase Is ☆☆☆★★
The phrase itself is enough famous.
But the propagator of the phrase is not Digital Monster.
And most of Japanese don't know it is used in the anime.

Fitness with Kamigawa ☆☆☆☆★
At first look, I felt this is not suitable for Kamigawa.
But Kaito is toting a racoon mech so this kind of kawaii beast might be there. And the art is from Digital Monster and it fit with cyber Kamigawa.

Role in Limited ☆☆★★★
I expect it is enough strong in limited.
In two points, I think it is especially advantageous in NEO limited.
At first, it can tap a vehicle.
After opponent's creatures crewed a vehicle, then tapping it gives you a huge tempo advantage. Depending on the case, it might be a clincher.
And second, it can tap an equipped creature. This case give you a good tempo advantage.
The problem is that equipment and vehicle are ones of NEO features and tapping them without tempo nor card loss may spoil those features.
It is common so this prevention occurs many times and I guess people would avoid vehicle itself in NEO limited.
Putting it simply, it is too strong in NEO.

{A Peaceful Slow Life/Idea }
Card Balance ☆☆★★★
It seems to be hard to handle the penalty and the transforming condition.
If you enchant it to 3 mana creature in accordance with mana curve, the enchanted creature has ward 3.
It is not so hard to kill it with one or two mana spell.
And opponent's creatures which are summoned after it, 4 or more mana creatures, would not to hesitate to attack you because they can win or draw against the enchanted creature in combat.
Supposing it was casted on 6 mana creature, ward 6 is reliable and can stop most of attackers.
But if you premise that you already have 6 mana creature, another 6 mana creature is preferable to this aura, I think.
Combo with Harm's Way or goad is conceivable but even with the combo, I can't help feeling it is closer to a fan deck.
I would give it some etb bonus such as search a plain or forest and put it into your hand, prevent all combat damage until next your turn, gain life, etc.

Flavor ☆☆☆☆★
The front face has a reclusive taste.
And the back face gives it the power and toughness that none can defeat in simple one-on-one combat.

How Famous the Phrase Is ☆☆★★★
Probably this is 異世界スローライフ ( Slow Life in Another World ).
This phrase is not so famous. Only known among who are very interested in manga and anime.
Even people who are modestly interested in them don't grasp the genre.
They regard whole of them as "another world" genre and don't know the subgenres.

Fitness with Kamigawa ☆☆☆☆★
In NEO, there are reformers of technology and conservatives of nature.
And there's a war, so the enchanted creature would be discharged from an army and get recluse.

Role in Limited ☆☆★★★
GW archetype in NEO is enchantment.
I think this card is nearly unplayable.
But white has some creatures with flying so it might be sometimes adopted into a deck which aim to attack with flyers during non-flyers are stalemated.

{I Want You to Be Happy/vizionarius }
Card Balance ☆☆☆★★
One time vigilance with cantrip for one mana is almost balanced.
In limited, it is useful to take advantage in damage race.
But it limits target to only damaged creature so it can be a dead stock in your hand if your attacker isn't blocked or dies with the blocker.
It has enough impact if you could cast it, but a bit difficult to use.

Flavor ☆☆☆☆★
Well expressed that she is cheering up a damaged person.

How Famous the Phrase Is ☆★★★★
Inuyasha itself is well known. Most people know the name and the author Rumiko's artwork.
But who really read the manga or watched the anime is not so many and the phrase is not well known.

Fitness with Kamigawa ☆☆☆☆☆
Only one failure on your card to "keep the true feel of the original card in the cycle" is that you wrote the original speaker.
But I try to see this sentence as though Kagome's name isn't there, then I feel this might be Kaito or the Emperor's word.
NEO has an aspect of a love story, so it fits with Kamigawa.

Role in Limited ☆☆☆★★
As I wrote before, "damaged" is not so trivial constraint.
WU deck might use it for it would have not a few creatures with toughness higher than the power and some draw-then-discard filters.
And it also provides a crewer for a vehicle after attack and WU is a vehicle color in NEO.

{A Lesson Without Pain/moweda }
Card Balance ☆☆☆☆★
Like vizionarius' one, the damaged constraint is not so insignificant.
+1/+1 counter has more impact than pseudo vigilance in many cases but it also means that you can't target opponent's creature without pain.

Flavor ☆☆☆☆★
Nicely expressing the flavor.

How Famous the Phrase Is ☆☆☆★★
Fullmetal Alchemist is very famous.
But the phrase is not famous so much as known by who didn't watch it.
But the word is told in the last episode of it and it has something to do with the theme of it, so probably modestly famous among casual fallowers.

Fitness with Kamigawa ☆☆☆☆★
It fits with GW conservatives in Kamigawa. Seems to be an old proverb in there.

Role in Limited ☆☆☆☆☆
As I wrote in vizionarius' feedback, damaged is a bit difficult condition to handle.
But Kamigawa has modify mechanism and especially RG archetype is modification.
So if your deck lacks modification parts, it will be considered to use.

{Winner}
Winner is moweda .
It is an one mana cantrip and has a relationship with modification mechanism.
And it also targets a damaged creature though probably it is more difficult to use than You Are Already Dead.
The runner-up is Flo00 for the innovative ability, and the third is vizionarius by a narrow margin.

{Spoiler}Interesting art and effect. Deathtouch feels very at home in both chosen colors and could have some interesting interactions with your creatures, namely those that might have first/double strike or trample or that can deal noncombat damage. The availability of those kinds of interactions is precisely what you want in a mutate creature, it's what makes the mechanic most interesting. While initially the effect seemed a bit undercosted, you'll generally only be mutating during your turn. 3 mana seems like a fair price for giving creatures deathtouch during your turn judging by cards like Bow of Nylea, and this requires multiple things being cast to keep giving it, making up for that difference of legend to nonlegend.

{Spoiler}You probably didn't need to raise the cost. Yes a +1/+1 counter is strong as it persists, but then so is an extra +2 to power. The counter is probably stronger overall, but the extra power could also win the game.

In any case, giving counters to your creatures is simic could give you some big synergies. Another minor bonus is that Ikoria where this mechanic came from was I think big on counters as well (it introduced keyword counters) and so this could have some extra synergy there.

{Spoiler}Both cards had some great synergies and good balance, though vizionarius had just the very slight edge in both regards, so they get the victory on this one.