A fairly trope laden isekai LN. Protagonist is overpowered from the start? Check, can use all magic? check, early harem setup? check, harem includes royalty? check, picks a katana as weapon? check. There's no real surprises here folks. The smartphone gimmick from the title is a handy McGuffin item. Allowing the protagonist to referrence the internet to look up things he doesn't know how to do, exploit it's mapping feature in conjunction with magic, look up new recipes to introduce new food items, all the standard things you often get when a protagonist is some kind of isekai prepper but instead is just a regular guy but still has access to google thanks to the smartphone cheat. I can't remember exactly what volume they get foreshadowed around 3~4 iirc, but volume 6 introduces mechas. So if you miss the earlier foreshadowing like I did and end up invested in the story having this addition really throws a wrench in the more traditional fantasy setting I prefer and goes full mech otaku. A feature that will be present in one form or another in pretty much every subsequent volume that I've read (currently have read up to and including volume 12). I've honestly debated dropping this series but tend to fall for the sunk cost fallacy and feeling that I've come this far, I might as well just keep going. It's still a fun story if you enjoy isekai series.