Headcanon;
Isono didn’t always know how to cook. Poor man could just about boil an egg and make a sandwich.
But when Gozaburo passed away, he started taking cooking lessons. From international dishes to desserts, he took them all and aced them. Because now that ‘the tyrant’ was gone, he wanted to try and give Seto and Mokuba the family love they deserved. He always made their lunches for school, without the boys knowing.
However, he would often practice his cooking at night, and Mokuba would sometimes wake up during the night and be lured to the kitchen by the smell of food. When Isono was particularly proud of something, he would let Mokuba try it. These nightly hangouts became a thing after a while. Even if Isono still scolded Mokuba that he had to go to bed because ‘’You have school tomorrow Mokuba-sama, you’re a growing boy you need your sleep! Now off you go!’’.