The concept is complete otaku wank. It's a first-person camera narrative, in which you play Silent Protagonist who manages to win the heart of a girl without saying or doing anything that we can see. You then do it twice more. (There are three girls in this show and you cycle through them.) This show's target audience is the kind of otaku who doesn't go outside and says he's not interested in 3D girls.
In other words, it's an abomination. We should be lining the streets to protest against it.
At the same time, though, it's also quite good. If you can forget the show's purpose, then in practice it's a lot like a one-woman stage show. There's only one speaking character in any episode and it'll all be about her. I actually quite enjoyed the show, albeit partly in unintended ways. Every so often it decides to have a bowl of creepy for breakfast.
It has male gaze and inconsistent first-person camera angles, you see. The camera often lingers on the girls' bodies... but since the camera is us, that makes us a pervert and a lech. Admittedly the show often breaks its own first-person camera rules, e.g. with shots where "you" aren't even present. However it's still common enough that lascivious camera angles are liable to feel if Silent Protagonist isn't at all the honourable gentleman that the show wants us to assume. When girls are inviting themselves into his flat late at night, it might feel alarming. The funniest, i.e. worst, example of this is the "Norman Bates in Psycho" shot in ep.7, when Natsuki's in the shower and the camera's slowly creeping through the bathroom towards her shower door. RUN FOR YOUR LIFE, GIRL! I want to see a parody edit of this anime that turns the Silent Protagonist into Jason Voorhees from the Friday the 13th films.
EPISODES 1-4: HANASAKA YUI
This is a perfectly reasonable little story, but she's also the least interesting of the three roles, because she has the shallowest issues. She wants to get into university, but she's not confident about her grades! Could you help her study? The plot unfolds exactly as you'd expect.
That said, though, the show's fairly serious about Yui's ambitions. She's not happy when you ask about her grades in ep.1, then she's in tears in ep.3 because she doesn't want to have to settle for her second-choice university. You find her asleep at her desk because she'd been trying to study all through the night. I think the character works, although it weakens her story to end by shoehorning it into an anime pseudo-romantic cliche. (It's credible and it makes sense for the character, but it's also so preordained that you'd have dropped dead with shock had the show given us any other outcome.)
EPISODES 5-8: NATSUKI MOMOHARA
Did I mention that this show can be creepy? Well, here's another example. Natsuki is your little sister, come to visit from Tokyo and expecting to stay in your flat. She'll offer herself to you sexually, straddle you for a massage and offer to become your girlfriend if you can't find anyone else, although it's unclear how seriously we're meant to take all those offers. That last one, for instance, is followed (after a beat) by "just kidding".
This adds a whole new level to the leering camera angles, obviously. Have you ever ogled your sister's arse?
That said, though, Natsuki's also the most entertaining of the show's three female characters, because she's got the strongest and liveliest relationship with Silent Protagonist. You'll squabble about what to have on TV. When she finds your pornography, she won't be gentle and forgiving like Yui was. She'll burn it. She's high-handed, peremptory and occasionally a bit tsundere. This really does feel like a brother-sister relationship, except in certain moments.
At the same time, though, she's genuinely worried about you and it looks as if she's right to be. You're overworking and you seem tired all the time. In one scene, you come home drunk and collapse. Natsuki seems perceptive about you (which shouldn't be surprising), while you're capable of hurting her by rejecting her help in an extremely final way.
I liked this story a fair bit, although I think we should be deeply scared by a little sister being presented as (nearly) a romantic choice in a first-person camera show.
EPISODES 9-12: MOKA AOSHIMA
She's your childhood friend and she wants to be a musician. She's also a failure. All she's released so far is one mini-album, so she's busking in the park and we never see anyone listening to her there. Meanwhile you're trying to be a novelist, with no sign that you've ever been published. It looks as if you're both heading for a painful collision with reality.
This is a fairly dark story and an unusual backdrop for a romance. A director criticises Moka for not being sexy enough and ask if she's ever had a boyfriend. (She hasn't.) We see rejection letters. "It's like being told you don't have a place in this world." Moka's slowly and painfully heading towards a decision to abandon her dream, quit the city and move back home. A little disturbingly, the romantic finale has you encouraging her and persuading her not to give up after all, which may or may be kindness.
OVA EPISODE 13: ALL THREE GIRLS
This is just a rerun of scenes we've already seen... but in swimsuits. It's funny because it's so ridiculous. "This is my school uniform."
In summary, I liked it but you've got to accept some disturbing anime-isms. It's "insert your face here" wish-fulfilment wank for losers who've given up on real romance and can only project their sexual desires on to pixels, with the ultimate passive protagonist. (He's not mute, but we don't hear his voice when he talks. We also never see him, of course.) It's also got multiple kinds of creepy. I'm definitely watching Season 2.
For its gender-flipped brother show, watch Room Mate.