Abby isn't the skinniest girl in the world. She's healthy, but to her, that's not skinny enough. That's average, and she doesn't want to be average. She wants to be skinny. So, she does what anyone who wants to lose weight does. She follows through with it. Only, not in a healthy way, like exercising or eating healthier. She just eats less. And less. And less. Finally, whenever she eats, however rarely it is, she pukes it up. No one notices, of course, they're too busy caught up in their own lives. Her mom is always at work, her sister is away at college, her friends notice, but don't bother her enough about it to change anything. Her dad isn't even a part of her life, anymore. He left when she was 10. When Justin shows up, she is in a bad place, and he is the only one who could possibly pull her out.
Kanda Kyoichi transmigrated to Konoha and became a temporary instructor at the Ninja Academy. Fortunately, he awakened the Mentor System.
By teaching others, he could earn rewards.
Thus began Kyoichi's career as a "teacher" in the ninja world.
Shisui: "Sensei's unique interpretation of the Will of Fire has given the Uchiha Clan a true sense of direction!"
Asuma: "The essence of the jade lies in protecting the people, with the advanced leading the way for the less experienced. Only then can Konoha become stronger!"
Kakashi: "He's my life mentor. He transformed Konoha!"
...
Years later, in the memoirs of Kyoichi, now the Hokage, he wrote:
"I honestly just wanted to be a life mentor!"