I didn't really know much about "Watcher" before I started watching it. In truth there's not all that much to know to be honest:
A couple moves to Romania. Husband works while wife sits around waiting for him to come home. Wife believes that somebody is stalking her and husband thinks she is going crazy.
It sounds ridiculously simple because it is. We've seen it before - HOWEVER - Okuno clearly set out to make a brilliantly executed suspense flick and did just that.
The movie is contained and everything in it is there for a reason. Cinematography and especially the sound design is incredibly well done and makes the simplest thing like shopping for groceries an unnerving experience.
And finally the biggest praise has to go to Monroe. She has come a long way from "It Follows" and here she brings this simple movie to life with outstanding (and very believable) acting that successfully makes you question her sanity. Hopefully she'll bless us with her talent in many more (horror) movies to come.
Now obviously "Watcher" isn't the perfect movie even though everything is done so well. The fact is that we've seen it all before - countless times - and Okuno plays it extremely safe here by taking no chances whatsoever. This makes for an underwhelming movie experience as a whole and will no doubt bore some viewers.
Do I recommend "Watcher"? If you love suspense - YES. To witness Monroe's brilliant performance - YES. If you're looking for a great movie - NAH, go find something else.