Here's the short summary the website had the girls name ks Hotaru and her mother's name is Azusa but it doesn't mention anything about a brain tumor but again its only a summary, I copy n pasted it so you could read it <3 your welcome 🤗
In an unknown snowy environment, a man had discovered the whereabouts of a secret hideout. After obtaining the information he needed, the man (called Seeker) later went to a bar run by Hotaru and her mother Azusa to meet with three colleagues named Mario, Chantha and Futoshi to report his findings. The three would then react with disgust and disappointment upon discovering Korosensei's various foibles.
Cutting back to when Seeker was gathering information, Korosensei was mortified to find that a person had found his adult "studio". He explained that he took one day a month to relax in his hideout, where he would not set a bad example for his students. After complimenting Seeker on finding his hideout, Korosensei packed up his hideout and relocated elsewhere.
Back in present day, the four assassins are briefly infatuated by Azusa, which made them (minus Futoshi) glare at each other in hostility. A poorly disguised Korosensei entered the bar and greeted the assassins, which triggered them to attack him. While Hotaru and her mother observe the fight, the former recalled that the octopus was a teacher and that she looked like one of his students. She claims that this is the blink-of-an-eye story of the winter she spent with these gentlemen.
