The supporting character's harem is very normal - Chapter 384 That is Worship Energy

Cosplayer Liu Mang accidentally crosses through time and arrived at the Eastern Han Dynasty wearing Aries Gold Cloth. (Saint Seiya!) He arrived on top of the walls of XiaPi right when it was about to fall to Cao Cao.

“Don’t kill me bro; I’m not working for boss Cao!”

“Hey! You’re slashing the wrong person! Boss Lu’s underlings are there! Not me!”

He accidentally saved Lu Bu who was tied up by Song Xian. He accidentally became the son in law of Lu Bu. He accidentally changed the history of the Three Kingdoms period.

When aluminum casted Gold Cloths are worn by generals like Zhang Liao and Gao Shun during the Eastern Han Dynasty, glistering on their bodies… When the soldiers in the camps are sporting mechanical crossbows… When crossbreeding of rice plants appeared on Lu Bu’s territory…

Liu Mang knows that a world belonging to Lu is coming.

- Description from Novelupdates

The moment when mercenary leader Kwang Hwi receives video game like abilities, the world is suddenly thrown into chaos. A thick fog envelops the Earth, bringing with it savage, otherworldly monsters. At the same time humanity has been rendered defenseless against this onslaught, as the strange fog turns most weapons to rust. With mankind spiraling towards oblivion, it is up to Kwang Hwi, with his new abilities, to save the world. Watch as Kwang Hwi leads his militia and becomes the last bastion of humanity. Will he be this world’s savior, or its conqueror?

The story of otaku building a harem! School flower, loli, wife, mother and daughter, mature woman, teacher, nurse, queen, all kinds of beauties, three steps to push a girl, five steps to a group, harem group, infinite warmth, so cool that you always need to prepare a tissue for easy reading !

- Description from novelbuddy

After a god screws up and accidentally takes high schooler Shou’s life, he offers him reincarnation with a gift to make up for it. Shou asks to retain all his old memories for the new life. Shou is reborn as Will, a noble’s son in a world where magic use is common and involves knowledge of kanji characters. With all his memories, he’s a brilliant toddler, and when he experiments with magic, he finds that he has an amazing talent for it! What’s more, though he was smart but unloved in his old life, in his new life he has a mother and a father who both love him deeply. His future as Will is looking very bright and cool!