Ok this show had an interesting hook off the jump. Kid is dead and God is sitting there saying sorry, my bad. So for the mistake of getting him killed, he gets him ready for a new world. He gets a buff and one request. That request is to keep his smartphone, hence the title. He comes to in the world and is a unicorn when it comes to magic. Where most people have an affinity to one or two, he is adept at all. Just a learning curve for him to bend anything to his will. His strength lies mainly in his use of null magic, which basically is anything as long as you know the spell.
This show is perfect for anyone that enjoys a overpowered character that is still learning. This is great show but doesn't top Overlord, but right behind it in premise. The design of this scream SAO, but we don't have that kind of story, sadly. It is one of those shows you can quickly binge on and would like it to keep going. Currently it's halfway through the season so you can't binge the whole thing yet. Check out this overpowered/harem show on Crunchyroll, or wherever you stream your shows.