Bodyguarding a Badass: After Loki challenges L and names Light Yagami as his future victim, L responds by forcibly taking Light into protective custody-a task that was easier planned then done since Light has a blackbelt in judo and doesn't feel he needs L's "protection" nor does he wish to put others at risk guarding him when he can take care of himself.
Boxed Crook: In this universe "Kira" is a hacker that works for the NPA to avoid prison time.
Celibate Hero: Light hasn't been in a relationship with anyone for over a year nor felt the need to have one.
Chaste Hero: L just doesn't get the whole relationship thing. Once when he was 16, and curious about why people make a big deal about sex, he had Watari procure for him the services of a couple of prostitutes. He never tried again.
Face Palm: when Sayu meets Light's "new friends" while insulting all of them:
Light sighed again, pressing the heels of his hands to his eyes. That migraine was assured now- damn all little sisters to the blackest pits of hell.
Fish out of Water: L sends Mello and Matt to spy on Light. Since they are in the middle of Tokyo, Light notices the blonde kid spying on him almost immediately.
Fix Fic: There is no Death Note so Light isn't as crazy as he is in canon. Also the author says it's not going to be a Kill 'em All ending like in canon however it's not going to be an Everyone Lives ending either.
Good Parents: Souichiro. When he caught onto his son's growing mental problems he "saved his life" by pulling him out of school and worked with him to help his mind heal, giving him training that actually stimulated his genius and encouraging him to experience more of the world and just be a teenager for a while. He also suggested Light take on a quasi-legal hobby like hacking in order to train him out of his growing Black and White Insanity.
Misa: Hello, Mr. Great Detective! Play nice with Raito-kun; he's a genius but a bit difficult. Oh, and if anything happens to Raito while he is under L's care, Misa-Misa will destroy him if it is the last thing she does!
I'm Standing Right Here: When Light and L begin speaking of Mello like he's a highly contagious disease while he's in the room with them.
The Sociopath: Light worries he would have become one had his father not caught on to his growing disgust with the world and intervened. Light still worries he might become one seeing as mental illness may have genetic as well as environmental components.
Unconventional Formatting: Matt's lines of code. He complains that Light is wasting time being neat when the router doesn't care. Light retorts that he often has to show his work to the NPA and this way it's easier to catch if you make a mistake.
Yandere: Takada. When Light began dating her in college they agreed it would be nothing serious since they both wanted to focus on their careers. But when Light broke up with her Takada did not take it well and has held a grudge for four years and seems to be out to ruin Light's career.