Yuumi will look to poke you down with her Q. When she uses it, run inside the minion wave so she cannot easily land it. Alternatively, if it’s safe to do so, stand inside the minion wave at all times.
Invest in an early Executioner’s Calling or a similar Grevious Wounds item to reduce her healing in lane.
Post level 6, watch out for Yuumi’s Ultimate R. Take deliberate care if you do not have vision nearby as her Ultimate R is a great ganking setup tool.
Yuumi’s R has quite a big area of effect. Do not look to team fight if her R is up inside the jungle or around an objective as she will be able to root multiple members of your team. Try to fight her in open areas where your team is not grouped to closely.
Yuumi’s play style allows her to jump onto any member of her team if they’re nearby. If the enemy looks to be engaging, back off as soon as they play aggressively especially if Yuumi is attached to the frontline as she will use her R aggressively to start the team fight.
If Yuumi is in a bad position, try to kill her. She has no mobility without her allies nearby and therefore can be punished very quickly.
Yuumi is strong once she has completed her first item. At this team, her healing and damage output will increase.
Once Yuumi is level 6 and when she unlocks her Ultimate R, her kill pressure increases. Back away if you’re low as she also has great gank setup at this time too.
Team fights are good for Yuumi as she can empower her carries. You’ll need to invest in an Executioner’s Calling at this time to reduce her healing.