If anyone still have problem not getting it, activate the windmill mechanism that's on the mountain so you fly up a bit, I did it with Xiao and got the achievement. Yeah, I failed a few times at first but I got it eventually.

For anyone attempting this and failing despite hitting multiple times like me. Stop using Kazuha. Chihayaburu/Midare Ranzan doesn't count as a plunging attack for getting this achievement. Made video, submitting as a bug.

As luck would have it, I got it first time. Thank you!

missed a bit and got the bird instead lol im so happy i got it on one try tysm

I can't get it?

It also works on the bird close to the whopperflower

i plunged for more than 5 seconds (6.14 seconds to be exact) and still did not get the achievement... >:V i tried multiple times and but still did not get a single achievement. is it my game that is broken?

Qiqi plunged. Qiqi accidentally killed it, someone told Qiqi that it would give cocogoat milk, there wasn't any

I missed, clipped a bird that was nearby and proceded to die to the plant... still got it XD