Very cute HxH doujinshi (it has two different stories), starring Gon, Killua and Killua's twin brother (supposely). For those who can't read japanese, I found a summary.

~~~~~~~~~ Story 1 ~~~~~~~~~

One morning before school, Killua wakes up to Gon by his bedside. He freaks out and Gon tells him that he's there because he kept on calling Killua yet there was no answer, so he came in. Gon then notices something in between Killua's legs and asks what it is. Evidently, Killua yells and gets Gon to wait outside. It is then probably confirmed what it is that Gon had touched, and the note at the bottom says, "Mornings for boys are awful."
As Killua and Gon walk to school together, Killua realises that he has yet to eat breakfast and takes out his mini chocolate snack. Gon snatches it away from him and Killua says that it is a very cruel thing to do. Gon that says in a very cute manner, "I'll let you have my wiener later so just bear with it now."

Killua, being himself, totally dies from what Gon said and comments on how pure Gon is.
The next part happens after school. Gon forgot something about his logbook and he has to stay behind. Killua stays behind too to wait for Gon but Gon feels bad about it and tells Killua to go home first next time.
Gon looks at Killua and realises that Killua is staring at him and he feels a little uneasy about it. He makes an excuse of having to go and get the logbook back. Killua holds him back and they inch close until Aruka suddenly interrupts. He says, "Gon-chan~ I waited for you but you didn't come so I came here...... What are you doing?"

Killua is annoyed at Aruka for suddenly appearing and threatens him saying that he has an embarrassing photo of Aruka with him and he'll show it to Gon. Aruka at first has some doubts, but Killua tells him that it's not a lie and he throws the photo out.

After that the pictures speak for itself.
Aruka sees the photo and whips back to ask Killua where he had gotten such a photo, only to have his attention moved onto something else. Killua and Gon decide to go home together and Killua mentions to Gon that his face is very red. Aruka is ignored.
Killua kind of apologises for being so sudden.
Gon smiles at Killua and then tells him he has a red face too. Aruka is still ignored.

~~~~~~~~~ Story 2 ~~~~~~~~

Gon received a candy drop from some girl from his class. The candy drop has a jinx, you're supposed to give it to the person that you want to be together with forever and that you like the most.
Gon thinks of Killua and gets a little embarrassed, telling himself that he didn't really mean it that way and Killua is his best friend. However, he still decides to give it to Killua. Gon thinks to himself that Killua likes sweet things.
Aruka appears. Gon accidentally drops his candy and Aruka picks it up and Gon thanks him for doing so, adding things about how dangerous this place because he may lose this important candy drop easily.

Aruka realises how important this candy is. He teases Gon and says that he will eat it. Gon refuses, so Aruka makes a deal to exchange the candy back with a kiss. Gon refuses at first, but he gives in in the end. Right before they really do kiss, Killua comes up from most likely cleaning duty and yells asking what they're doing. Killua yells at Aruka for being cruel and demands for an explanation. He also asks the same from Gon.
Gon apologises and Aruka sees just how sorry Gon really is (and probably also realises that the candy drop is for Killua). Aruka returns it back to Gon and explains the situation to Killua briefly. He then leaves.
Gon gives the candy to Killua and Killua is surprised at first, until Gon explains the meaning behind the candy to Killua and it seems that Killua is slightly softened for a moment and he accepts it... then stuffs the candy into Gon's mouth. Killua demands that there must be a mouth-to-mouth transfer of the candy drop. He tells Gon something like, "Did you think my anger would be gone so easily?" and then "If you think you've done wrong then transfer that candy drop to me so I can eat it."

And that was what happened except after it was transfered into Killua's mouth, Killua said, "Gochisousama (which is what people say when they finish a meal, it is a way to thank someone for entertainment or a treat)."
After this, however, the transfer was reversed and Killua gave the candy back to Gon through another kiss. Gon asks why that is, and Killua's answer is, "Because, I also wanted to give that candy to Gon."
Gon laughs and this doujinshi concludes: "Let's be together forever."
In the last box, Aruka questions himself about why he is so annoyed.