I am surprised to see some of the harsh reviews of this manga, because I consider myself a pretty picky shoujo fan and I really adored Strobe Edge. To summarize my main point, I think it bests most of its peers because of its characters' sincerity and the chemistry between the leads.

Story (9):
The storyline is standard shoujo. Cute girl and cool guy develop feelings for each other but have to overcome the difficulties presented by competing love interests. However the core emotion that the story captures is that of first love. While "unrequited love" definitely weighs in heavily, the author's strength lies in communicating Ninako's surprise and happiness as she discovers first love (even in the context of it being unrequited). The story has a much more natural development and pacing than some other shoujo, which is why I give it such a high rating. Minus 1 point for unnecessary crying, an abrupt ending, and a laggy, repetitive internal dialogue leading up to the climax.

Art (5):
Sorry not sorry. It's cute, but if I'm judging it against other shoujo I have to say that the characters lack distinction. Other readers have noticed this, too. Ninako's friend group are all drawn with the same face, but are told apart by their differently styled hair. The two male leads are identical, save for the fact that Ren has dark hair. In fact, he's the only character for the first ~30 chapters with dark hair. Otherwise, he would be lost in this sea of clones. Also, lips. Everyone seems to have had lip injections. Guess it's a style.

Character (8):
Best part! I have criticized other shoujo manga for having weak characterization, unappealing leads, or inexplicable romance, but none of that applies here! The lead characters have well-defined, realistic personalities. People who are not fans will call Ninako ditzy or stupid, but she is more accurately described as clumsy, naive, and endearing. At the beginning of the manga, I found her particularly refreshing. She confronts and owns her emotions early on, winning over the reader with her positivity in the face of rejection. Ren is also likable; he's cool and intelligent without fully succumbing to the "perfect guy" type. He displays his flawed logic throughout the series as he struggles in his relationships with his girlfriend, Ninako, and his former friend Andou. The relationship between Ren and Ninako is possibly the best developed one I have seen in recent shoujo, particularly because it develops out of genuine compatibility (as opposed to the tropes of delinquent/tsundere, hot prince/"plain girl"). Throughout the series, the surrounding company are all struck by the chemistry between Ren and Ninako, and slowly (even reluctantly) begin to root for them.
I've gone on too long about this subject, but I will also say that the supporting cast is well-characterized. They add to the story with their distinct personalities, which is always a mark of good manga.

Missing Shoujo Trademarks (7):
Shoujo is predictable, so I wanted to give a few shout-outs to this manga for omitting the following typical scenes:
1) The whoops-I-fell-in-a-completely-average-situation-and-now-we're-in-a-compromising-position moment
2) The you-had-your-first-kiss?-then-when-will-you-have-sex friend group conversation that is just so unnecessary
3) The I'll-wait-until-you're-ready-but-believe-me-I'M-READY conversation between the formerly promiscuous boyfriend and entirely inexperienced girlfriend
4) The transformation scene where the girl is thrown into a dressing room and emerges as a goddess finally worthy of her handsome, rich boyfriend
5) The unexpected cuddle session when the sick and delirious male lead pulls the unsuspecting female lead onto the bed in the nurse's office/at his home
6) The date to the fair where they ride the ferris wheel to have some serious conversation
7) The date on Christmas or New Year's
8) The date to the aquarium