Teen SKK being bad at remembering to eat regularly because they're used to skipping meals.
Dazai just doesn't register that he's hungry, his body doesn't alert him until he's grumpy and lightheaded and can't figure out he's hungry.
Chuuya, ignoring his body's signals because he got used to being hungry on the streets. He forgets he can now afford to eat what he wants, when he wants. So he'll go hours in a constant state of hunger.
The adults within the mafia noticing this and developing a habit of just supplying them with food whenever they get the opportunity.
Snacks at debriefing meetings. Mori ordering his security around like room service whenever they're in his office. Kouyou inviting them out to restaurants or for tea. Hirotsu questioning his life choices as he makes whole meals for two teenagers he supervising whilst they're on a mission outside Yokohama.
Ango constantly lecturing Dazai about the importance of a healthy diet whilst, unbeknownst to him, Oda slips Dazai a cookie because it's better than nothing in his eyes.
Chuuya wouldn't directly take food from The Flags if they offered it, so they made a game of sneaking snacks into his pockets and then denying any knowledge of it, when he found them later.
Their elders so often giving them food out of nowhere is part of why Dazai is comfortable begging for a share of his co-workers food at the agency. Who also usually give in to him because they know he wouldn't eat other otherwise.
Even Chuuya's subordinates will sometimes drop off snacks along with their mission reports because they know he hasn't left his office in a good few hours.
the true-est form of love must be sharing food -- you need food (and water) to live, to take that and give it to someone else is like saying 'i need you to live', its like taking part of your life and placing it in front of someone saying 'here, this is me' and letting them have it
that must be why when atsushi gets a pastry from the cafe underneath the agency's office, he eats half and gives the rest to ranpo
it must be why he snaps his cookies or popsicles or anything of the sort in half and hands the bigger part to kyouka
it must be why he takes the best parts of his dish when the ada is together and places them onto the corner of dazai's plate instead
or why he gives kenji all the parts from his bento box kenji commented on
or why he lets naomi take a bite of whatever he's eating
or why he places his food in the middle of the table when it's him and juni and they eat together as if their separate meals r just one big one
or why he brings extras from his snack runs to gingerly place on the president's desk before bolting
or why he packs a small extra bento box just in case kunikida stays behind again or overworks himself
or why he always happens to buy yosano's favorite snacks to share with her
or why when he meets runs into the black lizard he splits his food further to give gin some too
or why he brings any 'new' and interesting snack he finds for lucy to try too
or why he splits everything when he's with aku between them, why he sees him in the cold and rushes over to give him his cup of hot chocolate and wrap his scarf around him
it must be why he packs dazai's lunch or invites him for breakfast
why he hosts or proposes dinner or lunch together with the ada
why he spends all night trying to perfect kyouka and kunikida's favorite dishes
or why he spent so long baking a funny looking cake that probably didn't taste too good but ranpo liked anyway
or why he keeps junichiro's favorite energy drinks in stock even though kyouka and him dont drink them
or why he learns all the cute food designs naomi eyes
or why he keeps an extra portion of everything to give to kenji
or why he brings the president tea in the morning
or why akutagawa knows that when he cant bring himself to eat -- too worried about what will happen if he runs out -- he can go to atsushi for a cup of tea now and meal later if he's up to it