Blue-Colored Introduction is the first episode of the Brigadoon: Marin and Melan.
Marin Asagi, a 13 year old girl, is seen racing her bike with a man while delivering papers. She beats the man in the race, who is seen delivering milk. After heading home, Marin decides to carve her wishes into a tree. She wishes that she can be best friends with her classmate, Moe Kisaragi, forever, that her farsightedness goes away, that she receives better grades in class, and that better things happen to her family.
She then follows her "advisor", Lolo, and finds a stone in the wall. Marin dreads about what will happen, but takes the stone anyway. She is then confronted and scolded by a woman for carving things into her sacred tree. Marin then goes home to eat with her family who are very poor and meets with her family to discuss about being poor. After a brief meal, she heads off to school to meet with her friend, Moe. She asks why Moe looks so shy, but at this exact moment, a classmate named Isshin lifts Marin's skirt and gets it stuck in her straps. As Marin is called up to receive an award, Moe signals her that her panties are showing, causing Marin to scream in embarrassment. However, this is the moment when the sky changes and odd patterns are seen. Her classmates believe it was because she showed her panties, but it is because of something else. At home, a robot appears and chases Marin as she tries to flee, but just before the robot can kill her, she throws ampoule and a Monomakia named Melan Blue to appear and protect her.
He takes her to a ride at the carnival and hides her there as he fights the robot. The robot nearly kills Marin, but Melan destroys it and asks if Marin's okay, however she just asks if he saw her underwear.