It takes 6 spell casts for Kassadin's slow, Force Pulse, to become castable. If he levels up that ability, judiciously use your own skills while laning against him.
Kassadin deals mostly magic damage. If he's doing well consider buying magic resist items like Mercury's Treads and Banshee's Veil.
Each time Kassadin consecutively uses Riftwalk, he pays more and more mana. Keep this in mind as you chase him.
The stats shown here show several valuable Yuumi vs. Kassadin matchup statistics that may help you grasp the differences between the pair. For instance, Yuumi’s KDA ratio ([kills + assists] / deaths) of NaN is more than Kassadin’s ratio of NaN, indicating that Yuumi may be more central to her team's team fighting capacity than Kassadin. This observation is in large part caused by the differences in assists.
Yuumi typically has a significantly smaller longest killing spree than her foe does. Commonly, she receives less damage than Kassadin. This typically indicates different amounts of tankyness, but it can also indicate that the one champion has less agility and thus is unable to flee from further damage when poked or engaged.
Both League of Legends champions are great. Both champs have their pros and cons. In the game's current meta, Yuumi usually loses when taking on Kassadin, with a 45.4% win rate. Therefore, Yuumi makes a bad counter for Kassadin.
While Yuumi does have a much lower winrate than Kassadin, when on opposite teams, Yuumi also has a much lower learning curve that makes her a less complex champion to learn. You should expect to face a difficult match when picking Yuumi into Kassadin.
Additionally, Yuumi has a lot of CC and other utility, a similar amount to Kassadin. This makes her just as valuable during teamfights, especially when trying to counter champions with a lot of burst damage.
While there is not a single best champion in League of Legends, in Yuumi vs Kassadin matchups, Kassadin is the better champion with a much lower win rate, less champion complexity, and a similar amount of utility to help out your team members during teamfights.
Yuumi is a bad counter for Kassadin. Focus your strategy on keeping up your CS and destroying objectives. If you are able to do that, you should be able to stand on your own as Yuumi against Kassadin.
To learn all of the intricacies of Yuumi to counter Kassadin during both the laning and mid / late game phases of League of Legends, you should keep reading to learn a few extra tricks and insights into this matchup. If you listen to the build and suggestions presented here, you should increase your win rate significantly and be that much closer to League of Legends pro players.
Yuumi most often gets a lot less CS compared to Kassadin. Champs who on average don't take many minion kills often don't need much CS to be effective, such as sup champs. They are capable of scaling well off of their abilities and first items alone. Yet, champions with a lot of CS, such as hyper-carries, often require several high cost items to be effective. In either situation, try to do better than the values shown here to do well.
The most important items to focus on in your Yuumi versus Kassadin build include Shurelya's Battlesong, Ardent Censer, and Dream Maker. When Yuumi incorporated at least these three pieces in her build, she performed significantly better when facing Kassadin than with many other typical builds. In fact, Yuumi had an average winrate of 45.4% battling Kassadin with this build.
To have the greatest chance of annihilating Kassadin as Yuumi, Yuumi players should equip the Summon Aery, Manaflow Band, Transcendence, Scorch, Font of Life, and Revitalize runes from the Sorcery and Resolve rune sets. Of all the rune sets players chose for Yuumi vs Kassadin counters, this blending of runes resulted in the highest win rate. Moreover, these runes gave a 45.4% win rate overall.
By default, tips, stats, and builds on how to beat Kassadin as Yuumi are presented for all ranked divisions combined. To narrow the stats and builds to an individual skill level, you should use the selection menu earlier on the page.