is that hanyuu? from higurashi?

According to the pixiv tags, it certainly is. What's she doing down there, though, I wonder? (As a side note, this also had the yukkuri shiteitte ne tag, lol.)

just cover it back up, Miku, it's best to leave things like that buried

Took me a while to notice that she's not even holding the shovel with her hands.

Is there a tag for 'Joke Request', or a 'Explanation Request'?

Because really, -

Joke

My head.

Also: That's a spade, not a shovel.

Spades are smaller and are used more for gardening, while shovels are larger and used more for burying victims in the ground.

nananonina said:
Is there a tag for 'Joke Request', or a 'Explanation Request'?

Because really, -

Joke

My head.

I think Hanyuu is telling Miku that she cut her lifespan in half when she broke the leek. I could be wrong.

Has no-one else noticed how she's holding the shovel-spade-doowap?

If you ask me, Hanyuu's sudden appearance has literally "cut short" the comic. Miku will never find her treasure—oh the horror.
Hanyuu's "She broke it" points to the bottom of the fourth frame, therefore, which makes sense.
Meta-joke is meta.