The Detective is Already Dead - Chapter 8: One day, two years ago

On his usual way to home Mikado Tsuchio fell into a hole that suddenly opened on the ground. Just like that, Tsuchio falls in a different world, he lands on a Grappler Wyvern and manages to tame it.

Tsuchio decides just like that to live in the other world, the reason for his quick decision: he wants to make a monster girl harem.

The Immortal Path led to Longevity and Sovereign was heading in ease. When the Longevity was no longer in ease, all living beings were just prisoners. Conspiracy, internal strife, and the invasion of the others, all of it emerged together. 

In such a world, there was such a young man. He made his way upstream, stepping on blood, defying the emperor, destroying the various kings, and slaughtering his way through the hundred clans to form an Immortal Path towards the throne of Sovereign! The Immortal Path was endless, while the Sovereign was limited. He used his blood to forge his immortal legend.

- Description from Novelupdates

Getting the [Boosted Gear] is expected for Issei. What if he gained it a month early and another one as well? Let the Games Begin... IsseiXHarem (if it wasn't, it wouldn't be DXD). Now has a TVTropes page! Getting the [Boosted Gear] is expected for Issei. What if he gained it a month early and another one as well? Let the Games Begin... IsseiXHarem (if it wasn't, it wouldn't be DXD). Now has a TVTropes page!

In this world, there is the beautiful mutual and telepathy love.