Keep an eye on what chapter the game is currently in as Yuuki's strength and weakness changes every chapter. However, she should look to set up situations where she can take advantage of her 2 ATK on even chapters since it's her most impactful form.
Fighting people on odd chapters, even when she has a low chance of dealing damage, can be worth it if Yuuki is in need of a KO since she will have a chance to fight them the next chapter. It's also beneficial if she would end up in front of someone with 1 ATK or higher on an even chapter, and she has the star lead.
Saki's Cookie helps Yuuki keep her HP at full since she is most likely to take 1 damage on odd chapters due to her gaining 2 DEF, allowing her more opportunities to use her 2 ATK on even chapters.
Since Yuuki will find herself low a lot, and becomes -1 DEF on even chapters, Rainbow-Colored Circle becomes her best defensive card since it allows her to preserve her HP for when get gets 2 DEF on odd chapters. It also can't be used against her on even chapters well since she will have 2 ATK.
Treasure Thief is a good card to bring to punish people for fighting Yuuki on odd chapters, and potentially giving her a good card like someone's hyper.
President's Privilege will reduce the cost of both of Yuuki's hypers so that she is more likely to make a profit off of them.
Despite the card art depicting her getting bullied, Yuuki uses Brutal Prank well since she isn't reliant on her hypers, and it can heal her if she lands on it.
Since Yuuki isn't particularly reliant on any one card, she can use Gift Exchange to punish anyone who relies on cards.
Mimic allows Yuuki to potentially gain a better hyper
Lucky Sevens gives Yuuki a 25% chance to near guarantee the chance of avoiding people who were looking for an easy KO after fighting her on an odd chapter by rolling a 0 or a 7 for movement her next turn, gives her more potential to KO someone on an even chapter, and even makes her revive faster on average. However, it does make her 2 DEF on odd chapters not as good, and it reduces the chance of her evading 1s and 2s to a 75% and a 62.5% chance respectively from an 83.33% and a 66.67% chance.
Keep an eye on what chapter the game is currently in. Yuuki is vulnerable to being KO'd on even chapters since she will have -1 DEF. This can be exacerbated by fighting her on an odd chapter beforehand, where she is a minimal threat with -1 ATK, so that she is forced to defend at 3 HP or lower on an even chapter.
Fighting Yuuki on an odd chapter also allows the player to avoid being fought by Yuuki on an even chapter, when she has 2 ATK.