Set Details
Choice Scarf Chi-Yu functions as a fast and powerful attacker that can threaten many common Restricted Pokemon with heavy damage, including both Calyrex formes, Zamazenta-C, and Lunala, while bolstering its teammates' special damage output with Beads of Ruin.
Although Snarl is Chi-Yu's weakest move, it allows it to chip foes while shutting down many Restricted Pokemon offensively, including Miraidon and Lunala, and breaking Focus Sash, which is notably used by Flutter Mane.
Choice Scarf allows Chi-Yu to outspeed the majority of the format, notably including Calyrex-S and Choice Scarf Urshifu-R.
Tera Ghost allows Chi-Yu to avoid Fake Out and alleviate some of Chi-Yu's weaknesses; it particularly provides an immunity to Fighting-type attacks from Zamazenta-C and Iron Hands. Tera Fire can be used as an alternative on teams with priority-blocking measures such as Indeedee-F and Farigiraf to bolster the damage of Heat Wave and Overheat, including guaranteeing an OHKO against Brute Bonnet and Zacian-C with Heat Wave and against Flutter Mane with Overheat.
Teambuilding
Common metagame threats such as Incineroar, Urshifu-R, and Koraidon can resist its STAB moves and, in the case of the latter two, threaten to OHKO Chi-Yu. Raging Bolt and Iron Hands, due to their bulk and power, can also pressure Chi-Yu.
Without Tera Ghost, Chi-Yu is vulnerable to Fake Out from the likes of Rillaboom and Incineroar. Opposing speed control, in the form of Tailwind and Trick Room, can cause many threats like Urshifu-R, Ogerpon-C, and Ursaluna to outspeed Chi-Yu and take advantage of its weak defenses.
Additionally, Wide Guard users like Zamazenta-C and Lunala can take advantage of Chi-Yu locked into Snarl or Heat Wave.
Due to its lack of bulk, priority moves can threaten Chi-Yu severely, namely Aqua Jet from Urshifu-R, Sucker Punch from Chien-Pao after Terastallizing, and Thunderclap from Raging Bolt.
Strong partners for Chi-Yu include powerful special attackers, such as Calyrex-S and Miraidon, which can take advantage of its Beads of Ruin while threatening Urshifu-R and Koraidon.
Koraidon also pairs very well with Chi-Yu, as not only do they form a powerful core offensively, with Chi-Yu threatening Lunala and Calyrex-S and Koraidon threatening Incineroar and Urshifu-R, but Koraidon also provides sun to bolster Chi-Yu's Fire-type attacks.
Flutter Mane is another common partner for Chi-Yu, as it benefits from Beads of Ruin to bolster its damage output, while Flutter Mane can run Taunt to deny Wide Guard and Trick Room.
Chi-Yu also appreciates redirection support to alleviate its frailty, commonly from Brute Bonnet and Indeedee-F, which can also provide support with Spore and Psychic Terrain, respectively.