Ninja Style: Decidueye has been added to Pokémon UNITE on May 30th, 2022. Decidueye costs 2499 Gems but its available on sale for 1539 Gems for a short period of time. Active UNITE (アクティブユナイト) and Sports UNITE (スポーツユナイト) style Holowear for Aegislash were also added and they cost 400 Gems each.

Ninja Style: Decidueye

Who? Who? Who is that flying silently across the rooftops to dunk a goal? Ninja Style: Decidueye is now available in Pokémon UNITE!

Sources: https://twitter.com/PokemonUnite/status/1531077941190344705 and https://twitter.com/poke_unite_jp/status/1531168538513350657