If you're looking for manga similar to Nikoniko Connie-chan, you might like these titles.
Marvin is a somewhat dorky 8-year-old kid with a lot to prove. The bullies at school taunt him, his friends are not very helpful, and all he wants is to just belong. So in an attempt to solve his problems, Marvin gets an idea: Karate lessons! But even with a master sensei and a new gi, is Marvin destined to a life in Klutz-ville, or will he emerge Karate Cool and ready to take on all of William Clarke Elementary?
Lilico’s life in Japan is going well. She has great friends and is the captain of the school's basketball team. She’s happy! Then comes her parents’ news: they’re moving to America! Before she knows it, Lilico finds herself in Brooklyn, New York, forced to start all over. And that won’t be easy with her closest friends thousands of miles away or a school bully who immediately dislikes her. Luckily, anime-loving Nala and Henry eventually befriend Lilico and with help from them―along with her guardian spirit who looks a lot like her cat, Nicco―Lilico just might figure out where she fits in.
Kokoro found a strange machine in her basement, as well as a variety of problems to solve!
In the year 2020 it became possible to travel to the "electric monster world" using special portable telephones. Making friends and sharing telephone numbers with the "electric monsters" became popular among humans. Our protagonist, Shigeki, is one such person. Although he originally arrived in the electric monster world on accident, he became determined to travel the world with his new electric monster companion Kuribute, and make more new friends while he was there.
Follows Shiro Kyoda, a young boy from Tamiya City and a student of the Bandai Elementary School. Shiro is an enthusiast of plastic model kits and "Plamo Simulation", a plastic model battle game. Shiro's dream is to become the representative of Japan in the World Simulation Tournament and be able to fight in the finals in the Battle of Hobbytopia.