Taking a Nano Forge Through The Multiverse

Well, I died. Kind of a bummer, yeah. But! I did get a chance to reincarnate, much like everyone else in this world. Everyone gets the choice if they wish to parade again through another life, or if they wanted to rest. God's were all-powerful after all.

Transmigrated into the body of a Scientist from Highschool of the Dead, friend to both Shizuka and Rika. His ties with Shizuka were as they both took medical courses together, and Rika knowing Shizuka ended up meeting him. Because of this he had stayed in great shape, and had a perfect excuse to inject himself into the story, for when the world fell apart, he was worried about his airhead friend.

Seth our MC not only got the ability to travel to Waifu of the dead but also got a few wishes, with a pretty standard System.

(A few notes)
Not meant to be serious, just a random thought I got while playing Red Faction Armageddon, and when I spun on a wheel, this is the anime that came up out of the massive list of possible starting locations I had out.
MC is... Not a bad guy? Kind of an orderly chaotic will take people to experiment on them, but not on innocent life. But he is usually inclined to help. He will not, however, be stupid, villains get killed, unless they're either hot or actually deserve a second chance.
-Not a System Slave
-The system has no AI or Intelligence to it
-HE DOES have S.A.M. Which if you're confused about what that is, look up Fed Faction Armageddon and look on its Wiki about SAM

-Do note, that it says Harem, but not Romance. Why? Because I'm trash at romance, I'm using this novel as a testing ground to get better at it while taking tips and tricks like a true nerfer from readers on how I could make it much better, so Harem may seem kind of forced but I'll try my best. There will be variety in it though, not just going to have jade beauties that look the same other than their hairstyles.