I was reading an Ash in Hisui fic and got an idea.

What if the Giratina Volo used had the knowledge from the future of people it'd meet and stuff.

Ash shows up in Hisui and then when Volo summons Giratina to fight him, Ash is just like "Giratina..." in a disappointed tone.

Giratina just starts kinda chirping at Ash or whining or whatever as he changes sides and Volo of course gets angry. Just Giratina becoming very baby-like almost realizing that Ash is there. idk, i just think it'd be cute.

Alternatively, Ash could have Dialga give Giratina the future memories after it's summoned, resulting in the same thing.