he arrived at modern era, the world obviously more advanced than his time but the power of martial artists has regressed for some reason, so he never has to use full power to deal with them but the technology also didn't reach the point where it's possible for time travel yet, there's also the gate which monsters would come out, as MC trying to get used to the foreign world, he found out that world is the same world 1000 years later from where he's gone missing and the heavenly demon order has dissolved over 20 years ago because of an unfortunate incident and the remnants of the order is fighting among themselves, making it impossible to rebuilt the order, MC then proceed to take extreme measure to unite the people, punish his descendants based on their sins and regains the glory of the order.

between those activities, he also found out that the descendant who gave him the nano machine gave up on returning to the far future and send 3 mc's people holding the code to the location of time machine with hibernation, but some mysterious group is interfering with it (disturbing the hibernation), MC saw the recording of his descendant trying to make a time machine although he already take measures to send available device to MC, he unable to complete it in his time so he trying to create A.I by transfering his knowledge to a supercomputer (MC feeling bad after he saw the recording of his descendant crying in pain because he's nearing death), but something wrong must has happened as that A.I suspected to be in the hands of that mysterious group.

Among those problem, the creatures from the gates also become issue, MC found out those creatures who look similar to humans called the demon clan has been infiltrating human society to search for specific treasures which is necessary to ascend the empty throne in their world, MC happened to hold some of the treasures, after the battle with the current demon king who suddenly showed up after leaving the throne empty for a long time, MC found the truth in the dead memories that the current king has dissatisfaction with the former king about humans, the former king fond of humans while the current king think of them as livestock, as the former king injured in a fierce battle with other race leader, the current king take advantage of that and throw the former king into the gate of earth hoping he would be destroyed in gate travel or die among humans he likes, some time later, the current king curious about the former king and decide to confirm his death, but when he arrive at the earth he saw the former king still alive and adapted being human, MC see the truth that the former king is his ancestor the founder of heavenly demon order, the ancestor beat the current king until almost dead and kicked him back to their original world.

As the conflict with the creatures from beyond the gates solved, MC informed by them that the gates opened everywhere on earth is caused by damaged planet defense core, it's caused by the long standing enemies of them (from what I understand about their description, with white wings and such, they're angels, I'm not sure if their name is literally angel clan) they intended to take over the earth, MC decide to wipe out the enemies who caused disturbance on earth and repair the damaged defense core, while the mysterious group is up to something creepy again, as you can expect with bio-criminal company who use their advanced knowledge to do various human experimentation, they clone human, made genetically enhanced human (even 1 of mc's people kidnapped in his hibernation and wake up with modified body), creating nano bomb to control and kill people etc.)

MC eventually found the truth about the mysterious group, the descendant who created A.I is betrayed by someone who helps him, that traitor made the A.I fully free from human control and they ended up killing the descendant who already suffered from illness, but the greedy traitor wanted all advanced knowledge and decide to extract it from the descendant's brain, fortunately they failed, they has a purpose to create a god using the A.I, with angels involvement, they create a vessel for the angel's leader (maybe his body injured badly like the former king in their fight), the thing with combination of persona of A.I and angel's leader then show up bringing chaos to the world, even MC has a hard time fighting it, this is a rare time when he seems humane as he reveal his feelings that he didn't want to go to a new world, he didn't mind not getting stronger if he can return to his original place and then his ancestor (soul?) help him destroy the enemy.

MC then found the room with his descendant's brain, among the deceased's property, there's code for MC saying 'where our relationship began', MC realise the location of the time machine and go pick it at the place he first met his descendant, founding it means the permanent separation from this world timeline and he can't bring anyone back, they have emotional goodbye, MC told them to take care of the order, half of the planet defense core has been repaired, the gates stopped appearing on some continent, MC told them to cooperate with the demon clan to repair the rest of it, MC returned to his time and only 3 days has passed since he gone missing although he has spent a few months on that other timeline, he already emotional from separation with the future people, when he saw his lover again and others face overlap with his people that got leave behind, he teared and hug his lover for a while.

There's some side stories after that but it's fine even you didn't read it, some may not like it after all.

Its a little funny how unnecessary the entire conflict was. Even if he got s**ked into the future without a time machine, hes basically immortal. Could literally have waited for the invention before returning right on schedule.

Would of made for a less interesting story though lol

I would have loved for the novel to go more into the gate system rather than using it like 3 times in 200 chapters, all we got was new group shows up and MC beats/cuts a arm off and repeat for most of the novel. With that said the 2nd half of the novel and some of the extra chapters (I didn't like the zombie one) was good.

For most overpowered main characters they have something interesting about them but all you get in this one is, him being strong and liking to cut peoples limbs off which grows old if this is the second novel you are reading from it. We lost him getting new skills, getting new people (everyone is below him), and most of the novel is missing a big antagonist.

I think this novel should have been the middle part of Nano Machine. We would have had him not be so powerful and we could have seen him grow more rather than going up one rank and being stronger than everyone.