whenever I tried to talk to yoshitsune to complete the quest and receive the items it say "inventory is full" but when i checked my inventory it still has 20 more slots pls help

You might have 99 of the item the quest is giving to you, in which case the game won't be able to accept it. Try dumping items into storage.

As Penii suggested, it's either inventory or storage. From what I've previously encountered, prizes will be sent to "Setting>Presents" if inventory is full. And for stuff like Susanoo's Aramitama, you won't be able to start if your storage is full. Things may have changed over time though.

oo thanks

additional info for everyone, related to reward items:

viewtopic.php?f=15&t=8407