I Became the 1st Floor Boss of the Tower - Chapter 213

A series of short stories in the world of Toaru Majutsu no Index organized into chapters featuring Kanzaki Kaori as the protagonist, going around the world and space doing missions for the Church of Necessary Evil, however, there is more than meets the eye as each incident is connected.

One chapter was bundled with each limited edition release of the Toaru Kagaku no Railgun anime DVD and BDs, with all of them together being equivalent to a single normal Toaru Majutsu no Index volume

The world called out for a hero to purge it of a great evil. It received Broccoli Bunch, explorer, expert cleaner, occasional ghost-buster, and full time Cinnamon Bun.

Features include:

Talking enemies into becoming friends

Hugging menu boxes

Awesome overpowered skills (such as Cleaning, and Gardening)

Wholesome litRPG mechanics

And more adventure than you could shake a stick at!

Follow Broccoli on her personal quest to make all the friends. All of them.

Eight hundred years ago, Xie Lian was the Crown Prince of the Xian Le kingdom. He was beloved by his citizens and was considered the darling of the world. He ascended to the Heavens at a young age; however, due to unfortunate circumstances, was quickly banished back to the mortal realm. Years later, he ascends again–only to be banished again a few minutes after his ascension.

Now, eight hundred years later, Xie Lian ascends to the Heavens for the third time as the laughing stock among all three realms. On his first task as a god thrice ascended, he meets a mysterious demon who rules the ghosts and terrifies the Heavens, yet, unbeknownst to Xie Lian, this demon king has been paying attention to him for a very, very long time.

- Description from Novelupdates

I finally managed to kill the demon lord.