This is probably my comfiest recent rom-com manga, along with 'Kekkon Suru Tte, Hontou Desu Ka'? A solid 9/10 all around.
Is it original? No. But the pacing and overall atmosphere are so darn natural and adorable that it really doesn't matter. Out of all those new wave-y gyaru meets introvert dude scenarios, this one stands out with how refreshing and laid-back it is.
The comedy in 'Seihantai' is on point: the illustrations are both hilarious and whimsical, and the mangaka's creativity shines through a lot of the panels. Forget about chuckling, I've had quite a few hearty laughs from some ridiculous art depictions (the konbini toilet paper scene got me cracking up).
Character development is another thing that's done right. Don't expect some ultra-deep characterization here, but you know what - the cast feels REAL and just organic with the way the mangaka has built these teenagers.
Stellar pacing too, with as few fillers as possible - and even whenever there's fluff in front of you, it feels just right, not boring/forced/superfluous.
It does help that the side cast is also very endearing and well-represented, something not commonly found in the genre.
So far, so good - I hope 'Seihantai' continues in the same vein. It's a breath of fresh air and one of those wholesome manga pieces people of any age and mood can enjoy with a smile on their face.