I read a manga a few years ago, about a hero who died while fighting the maou (maybe even defeated him). I think he touched some artifact at that time which allowed him to relive his life with all memories intact. He vowed to avert all tragic events from his previous life. In his previous life he had 3 lovers and each lady died a tragic death, but by making sure each one stays alive he is basically building up a harem. However he ends up meeting his lovers and companions out of order and also people whom he haven't met in previous life. The ladies don't automatically love him (without past life's events happening) and MCs actions may be altering the world to the point where future is still uncertain.

I think the maou was impossible to beat because of the artifact. I mean, each time a hero defeated him, he made sure to prepare for it in his next life.

Anyone knows the title of this manga? Back then it was still ongoing. It's possible the manga is better in my memories than it was in reality. There might have been some mature content int the manga (events from MCs first life), but I'm not sure.

Sounds similar to Tsuyokute New Saga...

~4400 manga completed
~1700 ongoing...

Seems to be the manga I was searching for. I was listening to Useless Wizard recap on YT recently and it made me think of this manga. There are even plenty of new chapters to read.

Too bad WN version got discontinued and even deleted, could have been good material for japanese practice (WNs are easier to obtain and read with a dictionary than official releases).

While is not the one you are looking for, and is only in the beginning, I recommend Toki Majutsushi no Tsuyokute New Game .