Lake (レイク Reikku) is a student of the Hero Academy, one of the First Years under Foyfoy's teaching. He is Ross's brother, Cecily's son, and the best friend of Salt, setting out on an adventure with Lym to find him.
Lake is a short young boy with smooth jet black hair and bright red eyes. He wears a dark blue shirt and goggles around his neck, as well as a shoulder pad on his left arm. He also wears black shorts and red shoes, with a silver Hero's Emblem that has a blue jewel embedded in it.
At certain points he'll wear a more casual outfit that's just a black t-shirt with no accessories.
Lake is an excitable child that is incredibly airheaded. He tends to make rash decisions and say blunt, harsh things without meaning to. His stupid decisions and overconfidence are exemplified when he sets off nearly alone to look for Salt. However, despite this general denseness, he is incredibly smart, making near perfect scores on all of his tests.
Lake is introduced when he rushes out into the oncoming attack of a monster being challenged by Ross and Crea. He loses horribly and Foyfoy and Lym meet up with him, explaining the situation and the current missing status of Salt. Lake agrees to go with Ross and Crea to figure out where he is.
Lake explains the situation with Salt, revealing that some time ago, during a class field trip to the Demon World, Alba losing control of his mana caused the cave they were in to shift around. He had become sealed in a hole in the ground with Lym and kept talking to keep them both calm. When they both make it out safe, Salt immediately taunts him for this without being told--tipping off his weird behaviors.
When Lake goes to ask his mother, Cecily, for permission to embark on the journey with Ross and Crea, she says no and imprisons him--revealing that she's really lonely and relies on Lake for company. This prompts a baseball tournament that Lake gets defeated in, but she allows him these freedoms on sheer plot advancement alone.
After some chaos in the city, it is revealed that Lake and Cecily were sent forward in time by a "failed experiment" 1000 years ago, and that Rchimedes is Lake's father. He is older than Ross(by how much is unknown) though they hadn't met each other at all in a way that Lake was conscious of.
During this, Lake reunites with Salt again, however not for very long. It is soon after this that Elf November's plan with Dezember to reignite Rchimedes's soul within Lake's body comes to fruition, and the activated Mana Maker-kun is forced into him, corrupting his soul with his father's and creating the New Demon Lord. Dezember takes to training this new "Lake" as a Demon Lord, offering him quizzes and lessons. One of his first tests was to destroy a city, which he accomplishes by placing cat ears on all of the residents and forcing them to say "woof", displaying his personality.
Later, "Lake" is confronted by Salt and his former classmates and challenged to a battle in order to restore Lake's soul from the way it is melded with Rchimedes'. The battle continues as Salt surpasses him in strength and then they reach a stalemate as Salt enters the new Demon Lord's unconsciousness.
Rchimedes is pulled from Lake's soul after a brief moment and he wakes as himself again, to immediately face off against Dezember. Salt's Maker-kun responded and grew volumes to Lake's overwhelming courage and with that, they were able to defeat him, almost to the point of killing him.
In Volume 0, Lake is crushed by a falling rock with Cecily when they were out on a walk one day, leading Rchimedes to spiral out of control into madness.
Salt is Lake's best friend and counterpart. Though Lake can be somewhat harsh to him sometimes, their relationship is close, and they seemingly have been friends since childhood.
Not much is particularly known about Lym and Lake's friendship, just that they are best friends. She seems to be along for the ride for anything he does.
Cecily is Lake's mother and for most of his life, only family member. She is incredibly attached to him and he doesn't seem to mind, showing that he is very fond of her.
Ross is Lake's younger brother. The two have no real displayed relationship except that Ross is already a little attached to him, showing a strong desire to protect him. Lake has no memory of him.
As a student, Lake's only abilities seem to come from his powerful smarts and ability to retain information.
- Salt and Lake's name combine to form a location, similar to Van and Couver.
- Lake is Ross's older brother despite his appearance.
"Come, monster! You may think I'm reckless, but a hero doesn't run away!!" (Chapter 3, Episode 1)
"If I wake up to a friend trying to hug me with such sparkling eyes, I'll definitely avoid him!!" (Chapter 3, Episode 44)
"This has got nothing to do with whose son I am. You're trying to destroy the world, right? I told you, I won't allow that!!" (Chapter 3, Episode 47)
"Good grief! Beating people you don't like is something anyone can do, you know? But we are heroes!" (Chapter 3, Episode 50)