Yuumi is not just a passive attached champion. Actively contribute to your team by warding, poking with Q, shielding allies, and making quick detach decisions in dangerous situations.
For optimal effectiveness, playing as a duo with a reliable partner is highly recommended. Yuumi synergizes especially well with strong late-game ADCs like Zeri.
Maintaining survival by staying attached to allies is crucial for Yuumi. Survive with strong carry champions until the late game to dominate with overwhelming utility.