After Maxing Out the Tech Tree, I Learned a Hundred Ways to Kill Demons

The male lead is the youngest child in the Butterfly family and has been reborn. In his previous life, he was a respectable person (not really).

Because of an illness, he was unable to walk in his previous life, so all he could do was study. He was very gifted, and therefore learned a great deal about technology.

He brings the knowledge in his head to the Taisho era and uses technology to realize his dream of killing demons.

His long isolation from the world has made him somewhat extreme in personality. He's very irritating from the first chapter, and at least he's irritated the author.

Theme: Technology changes the world