Yugo has a great passion for CRT Television and refuses to upgrade to any other type. This coupled with the fact he owns a CRT store has resulted in Rintaro nicknaming him "Mr. Braun" after the inventor of CRTs, German physicist Ferdinand Braun and the common Japanese name for CRTs, "Braun Tubes".
While appearing as a tough and menacing man and often using this demeanor to jokingly bully Rintaro, Yugo actually has a soft spot for the lab members and cares about their well-being. His daughter Nae Tennouji is his top priority and he will go to desperate lengths to ensure her safety.
Yugo has a bad temper, and is very easily annoyed by Rintaro's mannerisms as well as his "experiments" upstairs. He would never hesitate to even hit Rintaro and regularly threatens to raise the lab's rent money should the experiments continue to disturb him, though this has never actually happened.
In the presence of both his daughter and Rintaro, he would often attempt to "protect" her from Rintaro, whom he sees as a "pervert", though he was likely joking.
As Rintaro and Moeka visit him after they discover he was in cahoots with the Rounders to have the IBN5100 shipped to France. At first he never has qualms to silence them after he admits himself as FB, Moeka's superior but after Rintaro calls him out on dishonoring his close friend and mentor, Suzu Hashida's memory and revealing her to be the same Suzuha Amane from 2010 who hates SERN for creating their own dystopia in the near future. Not only he understands he will be deemed expendable for SERN, he also has a sense of honor and gratitude as he suddenly realizes his immoral decisions working under the organization then learning about Suzu's true identity and decides to commit suicide to make sure that SERN don't harm Nae and Moeka for their cause of safety.
Yugo was an orphan living in Paris. He grew up living a rough life in the sewers.
After seeing a gellified human in the sewers he was residing in, he was recruited by SERN, which provided the money he needed to get out of the slums. After a while, SERN ordered him to go to Akihabara in Japan. It was here that he met Suzu Hashida (his neighbor) and Tsuzuri Imamiya (his future wife).
Sometime prior to the first D-Mail, Tennouji recruited Moeka Kiryu into the Rounders and communicated with her under the code name "FB". It was only when Rintaro and Moeka discovered his identity that FB was revealed to be a man, as he introduced himself as a woman to Moeka, and used female phrasing. Yugo explained that he took up the exterior and identity of the one the recruit needs the most, so as to gain their blind and absolute trust and use them to no ends.
For the first half of the story, Yugo only appears as a mean landlord to Rintaro. However, when Moeka gets cut off from FB, Rintaro decided to work with her to track down FB, who turned out to be none other than Yugo himself. The three had a brief conversation before Yugo, realizing not only his usefulness to SERN has run out and that Rintaro tells him that Suzu is actually Suzuha Amane who came from the future to stop SERN creating their dystopia and he was dishonoring her memory all those years, he draws a gun to his head and commits suicide, much to Rintaro and Moeka's horror.
When 1% Divergence is obtained, Yugo is seen running his shop, having apparently never worked for SERN in this attractor field; but as the story of Steins;Gate Zero unfolds, Okabe confronts him and forces him to admit that he is indeed still a Rounder. However, he is viewed as an ally this time because he wishes to protect Nae from the danger she might be in after seeing the faces of shadowy attackers.
Yugo thus protects Kagari and Suzuha by having them work at his shop, and briefly uses his interrogator skill to help Okabe out in finding out who is after the former. It is hinted that he is far more ruthless and less redeemable, as he never encountered Suzu Hashida - since Suzuha traveled back to 2010 and not 1975. How much exactly his personality differs in this regard is unknown, however.
In the anime, Yugo shot and killed Moeka before killing himself.
Yugo appears as a side character in Steins;Gate and most subsequent spin-offs, with the exception of Braunian Motion of Love and Hate, in which he is the main character.
- In Robotics;Notes Mr. Braun is still alive and as doting on his daughter as ever in August 2019 in the Steins Gate world line.(1)[Citation Needed]
- Yugo's call sign of FB is the acronym for "Ferdinand Braun". Yugo himself confirmed this shortly after Rintaro discovers his identity.
- If the cosplay addon is activated in the Steins;Gate visual novel, Yugo's new appearance resembles the character Doraemon, albeit colored green instead of blue, and would appear as if he was bare-chested.