Would Ahri's Charm slow down Master Yi while he is using his ultimate?

Solution 1:

As you can see in the video, Yi is both charmed and slowed.

My opinion: Since walking slower means less forced movement (often an advantage for Yi), I doubt this will be changed in a future patch.

Solution 2:

The expected behaviour would be for Yi to walk full speed toward Arhi when Charmed.

Nevertheless, there is/was a bug where Yi would stay unaffected by the Charme (neither taunted, nor slowed)

Also, I read that "Charm" is a new type of CC effect. Thus master Yi is not immune to charm. This charm having the effect of slowing is not a trigger of a slow CC. Thus Yi is affected by both effects. It seems that this is meant for such champion not to walk too fast when going back, which could make weird behaviour like running past the charming champion.