Mun’s Theories:

who cooks normally?: Hakuba. He’s been trained, is good at, and enjoys it, though I believe Heiji would learn to cook his Osakan favorites because he thinks Hakuba can’t do it right for some reason.

how often do they fight?: Every. Single. Day. Usually nothing serious, though. I think the constant bantering keeps the pressure fairly low. 

what do they do when they’re away from each other?: Work, probably. I bet they both do a lot of work. All the time. Together, not together, just working. Heiji keeps up Kendou, though, and Hakuba probably has some sort of stupid hobby… 

nicknames for each other?: Heiji’d call Hakuba “Damn Prat” and Hakuba would call Heiji “Savage Brute” — hey these aren’t very nice, are they? 

who is more likely to pay for dinner?: They fight over it because they’re both spoiled rich kids with hearts of gold. 

who steals the covers at night?: HEIJI. THAT BASTARD. 

what would they get each other for gifts?: Books. When they get their own place it’s almost nothing but bookshelves. 

who remembers things?: Hakuba, definitely.

who cusses more?: It’s about equal, at least when they’re alone together. Otherwise, Heiji. 

what would they do if the other one was hurt?: Freak out and transform into the Mamma Bear or Mother Hen that they are. All of the cuddling and gentleness. 

who kissed who first?: Heiji kissed Hakuba first, while they were drunk. Probably because Hakuba was saying that Heiji’d never do it. 

who made the first move?: Once the kiss happened it was all over and Hakuba ATTACKED~ 

who started the relationship?: Heiji, since Hakuba was too shy to, oddly enough.

Hakuba’s Thoughts: 

“Hattori-kun? Well… I suppose he is rather attractive, and we do have much in common… I’m not certain that it would be the healthiest relationship ever, though, given my tendency to bait him.”