seems they're hiding something...

Cirno and Daiyousei are playing one of those hand games that elementary girls play. The song they sing is their own version, although in Japan there are also many different kinds of the same song.

I added the fourth line in the notes on the first panel to complete a sing-song, poem-y feel to it. Literally translated, it would be something like this:

Right next door,
The grandma and grandpa,
Eat sweet potatoes and fart,
With the power of fart,
They fly in the sky.

Though by adding that line in the first panel, it kind of feels like you're spoiling the punchline (such as it is)...

I saw the punchline, so to speak, as more evident in line 3, but you have a point. I'll take it off then.

I was just bored and tried to make it rhyme, hehe.