I tried to understand the commentary by using a translation machine. Not sure if the April Fool the artist made was to sell a doujin for 14 300 Yens, or if it's something else.

If i'm seeing this right i think kaga is holding a marriage registration waiting for zuikaku to sign with zuikaku (With tears of joy) ready to sign it.

gregoris said:

If i'm seeing this right i think kaga is holding a marriage registration waiting for zuikaku to sign with zuikaku (With tears of joy) ready to sign it.

That it is; furthermore, Tiny-Kaga's on the 'wife' side on the form.

and if you look closely too, Shoukaku was holding Zuihou as hostage if Zuikaku dared to accept it

Pffff what the.... happening

So going by what's been said:

So... Hiryuu looks proud. I assume she's the one who helped Kaga on the Marriage registration.
Souryuu is looking at Hiryuu, upset because i assume she's angry that she(Hiryuu) helped her with that despite the fact that Kaga's still a child.
Akagi is... well, Akagi looks like she doesn't have a care in the world, eating bauxite.

Shoukaku looks like she's completely against Zuikaku signing the Marriage registration and is threatening Zuikaku not to sign it by holding Zuihou hostage.
Zuihou unknowingly was dragged into the mess. Probably wondering "Why me?!"
Zuikaku looks eager to sign it but she's conflicted to do so because of the situation her sister made(?).