So again gents using logic. If garp is doing all the fighting exactly why did shiryu take it upon himself to kill koby with his invisibility fruit?
1. He saw that apkiji could not beat garp 1v1 and created an opening for him to hinder garp
2. Koby was occupied in assisting and shiryu could not have that happen
Or
Shiryu simply don't want to be useless like Smoothie. Someone top tier just attacked their turf, might as well do something.
Or
Shiryu want to join the fight, 'cause you know, he has a blood thirsty sword.
Imo, if the problem is Garp, it would be more effective to sneak attack Garp and not Koby.
This is more like Shiryu knows Aokiji can deal with Garp so he'll deal with the weaker ones.