Shirihama Kenichi is a weak scaredy-cat, and his status as the karate club's punching bag has earned him the name of ‘Weak Legs'. One day Kenichi meets Miu and, impressed by her skill after she effortlessly throws him to the ground, he follows her to the Ryouzanpaku dojo. There he finds five great masters of martial arts, and driven by his desire to become stronger, he begs them to accept him as their student - though it won't be easy. Kenichi endures harsh training (and injury) from Akisame - the philosophizing Jujitsu master; Apachai - the Muay Thai ‘God of Death'; Kensei - the ecchi Chinese Kempo Master; and Shigure - the weapons prodigy. Finally after proving his determination, he is accepted by Shio - the 100-dan Karate Master, who had initially wanted nothing to do with him. Now Kenichi walks the long and arduous path to becoming a master himself, all whilst trying to protect those he cares about from anyone who would dare to harm them.
These two manga are very similar, and not just because they are about martial arts. They have a very similar feel to them. Both Otawa and Kenichi in the pursuit of getting stronger, end up in dojo's that are more than they expected, and they both have super strong grandfathers running them. They both have a love interest in the granddaughter, whose also a strong fighter, and both of them have to go through intense, and strange training, in order to get stronger. Although Strongest Disciple is a bit more comedic, and seems to cover a wider variety of martial arts, if you liked one, you should try the other.
If you liked Full Contact or History's Strongest Disciple Kenichi, you'd like the other because they both are about martial arts. They both also chronicle the quest of the main character to become stronger with a "monster" martial artist as the head of the dojo. They each also find a love interest in the daughter/grandaughter of the Dojo head, which causes the Dojo head to make them become strong.
Minoru Kohinata has just become a student at Reinan University, a learning institute known for training Olympic-caliber athletes and martial artists – not for its academics. Having been kicked off the gymnastics team, Minoru’s only link to his former sport is his long-time friend Nana. But after trying to protect her from harm and being saved by the ruthless karate expert Ryuuji Mutou, Minoru finds himself quickly involved in the 2nd Karate Club, eager to finally become stronger.
If you liked Full Contact or Karate Shoukoushi Kohinata Minoru, you'd like the other because they both have a basis in martial arts. They both center around somewhat shy individuals that start karate and become good at it. As the stories develop you see how each trains with their friends and gets stronger while develping rivals.