C'mon Digimon

Clockwise: Deathmon (top left), Shinichiro Josaki,
Makoto Abe, Kentaro Kamon and Bun

I am big fan of Digimon. For those not in the know, Digimon was a series of virtual pet toys that got adapted into an excellent anime series that ultimately ended up becoming more popular than the toys. Digimon has a long history of manga.The first Digimon manga was "C'mon Digimon", which even managed to predate the anime series.  I am basing this post on an English translation of the comic. So if I get something wrong, that is probably why.
Plot
After winning a battle with 3D Digimon battle with his Deathmon Digimon, an unnamed kid smashes his opponent's dock. Makoto Abe, the narrator, explains Digimon are virtual pets that can fight each other and evolve into new form depending on how they are raised, and that the actual device is called a "dock". Makoto tries to befriend Kentaro Kamon, the only kid not interested in Digimon. He attempts to get Kamon interested in Digimon and fails. A classmate reveals Kamon seems to hate animals because he was bitten by a dog. After school, Kamon finds a Digimon Dock  and has every intent to just give it to Makoto. For some reason, Makoto decides to show Kamon a machine that temporarily turns Digimon into real creatures, which he demonstrates with "Kamon's" Digimon Bun. Yes, he has a machine that turns Digimon into living beings. This is not explained beyond his brother (a college graduate) being the one who made it. The next day, Makoto loses to the Deathmon-using kid, Shinichiro Josaki, in a battle using the 3-D Coliseum, a table that turns Digimon real so that they can fight (similar to Makoto's machine except the Digimon are smaller). Shinichiro is a rich kid that smashes the docks of people that lose against him because he is a jerk. As such, he smashes Makoto's dock. Seeing Makoto emotionally distressed about a toy he could probably easily replace, Kamon agrees to fight Josaki in 10 days. Kamon and Makoto use this time and their machine to train Bun. During this, Kamon bonds with Bun, who doesn't evolve even though he should. Before he fights Deathmon, Kamon learns from Shinichiro that Bun is actually "Badmon" (a rare glitch Digimon, that appears once per every 100,000, that is unable to evolve). During the fight, Shinichiro uses Deathmon's ability to change into forms (which are fusions of Deathmon and one Digimon he defeated) to toy with Kamon. Shinichiro finally uses a fire form to remind Kamon of his dog dying in a fire. Yes, Shinichiro is so much of a jerk that he did research on Kamon and decided to torment him with this traumatic memory.  However, Kamon reveals the dog died saving him. The memory of this allows Kamon to gain a second wind. This allows him to win. Namon is now interested in Digimon despite the fact Bun isn't useful in normal 2D battles (for some reason).
Influence 

Greymon

"C'mon Digimon" managed to leave its mark on the franchise. Namon was the inspiration for Taichi Yagami (the protagonist of the other pre-anime Digimon manga Digimon V-Tamer 01), who was the inspiration the lead character (of the same name) of the first anime series Digimon Adventure, who influenced every other Digimon anime lead character. Greymon was drawn in a way that wouldn't used again (since the Digimon didn't have official designs yet). This appearance of Greyman was used as the basis for Veedramon (the lead Digimon from Digimon V-Tamer 01).
References:
http://manga.animea.net/c-mon-digimon-chapter-1%20[Oneshot].html (click on the image to see more)
http://tvtropes.org/pmwiki/pmwiki.php/Manga/CMonDigimon