Dulluma appears in the Academy Shortcut in Downtown Springdale. Another way to find Dulluma is in Gates of Whimsy.
Befriended(Yo-kai Watch):"Ugh... That was so dull. But you? You're pretty cool."
Loafing:"Do I have to...?"
Receiving food (favourite):"Mmm..."
Receiving food (normal):"So-so."
Receiving food (disliked): "Hard to eat..."
Dulluma's design is based on a daruma doll, a wooden figurine representing Bodhidharma, the Buddhist monk credited with bringing Zen Buddhism to China, famous for being so dedicated to religious practices he'd give up all his limbs for their sake. They're sold at temples with blank, pupil-less eyes, because the owner will then draw in one pupil when setting a personal goal, then the other when they achieve it, so that the "incomplete" doll will remind them of what they set out to do every time they look at it. After New Year's the dolls are taken back to the temple and burned in a sort of burial rite, after they're thanked for their services.
Perhaps as a humorous twist, Dulluma makes people lazy and listless, instead of focused on their goals.
"Dulluma" is a portmanteau of dull and daruma. "Darudaruma" instead combines with darudaru (sluggish, languid).