Mobile Phone Beast Telefang summary:

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.