Azusa Aizawa, a 27 years old woman, died on work site due to overworking. She has the possibility to reincarnate, and so she plans to live a chilling and calm life. But will she be able to be relaxed?

After dying of overwork in the real world, I'm reincarnated as an immortal witch, and I spend 300 years enjoying a relaxing life. At some point, though, I end up at level 99. All those years spent killing slimes to make the money to pay the bills gave me a ton of experience points. Rumors of the level 99 witch spread, and soon I'm up to my ears in curious adventurers, duelist dragons, and even a monster girl calling me her mom. I've never been on an adventure, but I'm the strongest in the world... What's going to happen to my relaxing life?.—Crunchyroll

After dying from Over-Working, a newly reincarnated Office Worker spends 300 Years of her new Life in a Fantasy world Relaxing and taking it easy, only to find out she's accidentally been building up her Power & becomes the Strongest being in the World.