Actually, there's a "knife scene" at the very beginning of episode 1 (the opening scene of the drama).…
I already guessed that Sakura is the stalker of Mariko's mom but the theory of him being the killer of Mariko's mom... I haven't think of that. We got to know Hatano's main target is Sota so about the scene in Episode 1, Hatano used Mariko to lure Sota out and that's why he came with the knife. My guess right now is Sota wouldn't kill anyone and the blood scene is another trick to deceive us.
It's a dark psychological-thriller drama, that happens to "poke fun" at some cheap rom-com type settings.…
You look so stupid. First, you compared two drama which differ completely. When people pointed it out, you started being dramatic by saying we're enjoying psycho. We're enjoying the drama progress and mystery not psycho lol.
I like that the tension from the first episode still active and the suspense is interesting.