By "forward compatible with iron" it means you can't turn lead to steel by adding neutron, protons or electrons (e.g. Energy) like you can inside a nuclear reactor.
Standard Isekai Harem <-
Tropes that are inside include: evil characters are mysteriously able to sneak anywhere anytime, All female characters serve only as foils for the story, plots simple enough to be seen through by a child are completely opaque to the "smartest" people in the story not the MC
I opened it up after a few months happy to read some chapters and saw the [END] tag, but I loved the finish of this manga! A wholesome story start to end and with such a touching ending that felt just right.