While not as good as the anime adaptation of this story, the manga "Onegai Teacher" is still an interesting story with engaging characters.
The design is well done, the character models were all realistic and unique; each character was their own person.
The story is not nearly as developed or contain as many plot twists as the anime; it seems the anime added many scenes to the manga. However, the story does provide the essence of the "Onegai Teacher" story; the struggles of Mizuho and Kei as they deal with their love for each other.
The characters are interesting, Kei and Mizuho both grow and develop over the course of the manga. However, also unlike the anime series, there is less focus on the subsidiary characters; Koishi and the others are not developed or fleshed out as much as they are in the anime.
This manga is extremely short, and I think that the story comes out much better in the anime, with its added scenes and conflicts, than here in the manga. I probably will not re-read it, instead I will rewatch the anime.