From a certain author's perspective, the world he lived in had always been a boring uninteresting place. If asked if he could name one good thing about it, he probably couldn't. Up until forty, he lived in complete isolation and solitude, but he never once regretted or felt dissatisfied about the kind of life he lived.
But despite being content with such a lifestyle, it seems some god... or perhaps some busybody devil galavanting about playing pretend god was immensely dissatisfied with the way he lived his life and wanted to play a sick joke on him by sending him back to his first day in high school after he died a mysterious death.
Approached by a suspicious red-haired girl shortly after awakening and recognizing where he was, he's abruptly given a second chance at a youth filled with romance.
But what does this forty years old man turned sixteen do when confronted with youth? He flips youth off and tells it to take a hike, he's having none of it.
If there was some sort of godly existence watching over him from somewhere unknown, their only natural reaction would be to facepalm and question what was wrong with this incompetent romanceless idiot who knew nothing of love.
Low fantasy only really starts to appear around volume 3.
Presently there are 7 volumes for this series totaling about 850k words.