It was the year 845, Y/N Alert, Armin Alert's elder sister had been on Scout leave due to physical injury and her mind became a little unstable. When Titans infiltrated Shinganshina something clicked in her mind and she back to being the soldier she was. Levi Ackerman hears that Y/N had put her uniform back on and protected citizens as best as she could. He felt proud and instantly welcomed her back, but never showed it, when they were reunited after the 5-year training Y/N redid after the years she wasn't in the scouts. ▪Based on the manga more than the anime but added my own storyline