No premiere date announced yet. The new PV is here. Check out the ANN article for additional information. Synopsis for the first season from AniList:
Naofumi Iwatani, an uncharismatic Otaku who spends his days on games and manga, suddenly finds himself summoned to a parallel universe! He discovers he is one of four heroes equipped with legendary weapons and tasked with saving the world from its prophesied destruction. As the Shield Hero, the weakest of the heroes, all is not as it seems. Naofumi is soon alone, penniless, and betrayed. With no one to turn to, and nowhere to run, he is left with only his shield. Now, Naofumi must rise to become the legendary Shield Hero and save the world!
Yeah, it’s kind of like someone (presumably the light novel author) said, “Hmm, should I just put a timeskip here until the next big bad comes along? But then the series will be shorter and I’ll lose money . . . oh, wait, orphans in these stories always turn out to have some kind of important background, right?”