The supporting character's harem is very normal - Chapter 77 Controlling the Thunder Element

Baek Yigang is a son of the Baek Clan, one of the seven great clans of Zhongyuan. Afflicted with the Taiyin Qi Blockage, he is cursed with a shortened lifespan and the inability to collect internal energy. He had been peacefully spending the rest of his days indoors when he was ambushed by a group of masked people. During the ambush, he lost his servant who was like a sister to him. Chased by the attackers, Baek Yigang escaped through a secret underground path. When he came across a blocked path, he decided he’d at least die fighting and picked up a rusted sword that was stuck in the ground…

Never had the Radcliffe family expected their son-in-law, a loser in their eyes, to be the hidden Dragon Lord who had lived for myriads of years...

Three Days of Happiness is a novel by Sugaru Miaki, also known as Fafoo. It’s a rewritten version of the story originally posted to 2ch.

The premise of the story revolves around a shop where one can sell away the remaining years of their life, and the consequences of doing so.

“I Say A Little Prayer” is a short related story which was posted along with the novel’s release. It spoils some things about the main story, but nothing major.

Power and desire, money and strength, conscience and responsibility, the road ahead is at a loss, as a time traveler, Simon, where will he go, this is a leading mainstream novel with a relaxed daily life and a slow pace

- Description from novelbuddy