>When you save the Dynamaxed Tsareena at Turfield Stadium, Milo takes it in.
>If you see him on the Isle of Armour, he’s with Tsareena instead of his ace/first Pokémon like all the other characters there
>After you beat the Galarian Star Tournament, he swaps out Bellossom for Tsareena
Soul. Milo takes in a Pokémon that was misused in some shitty scheme and gains its trust until its comfortable battling with him. It also fits the fact that Milo changes his team the most of all Galar leaders, changing his ace and dropping Gossifleur (rather than evolving it like Nessa’s ‘mons) and also having version exclusive teams.