Kyōko Koizumi
Although his own leader albums failed to receive public attention, Kobayashi garnered commercial success in collaboration as producer or songwriter with other artists. As an arranger of his own composition "Anata ni Aete Yokatta" co-written and performed by Kyōko Koizumi in 1991, Kobayashi won the 33rd Japan Record Awards for Best Arrangement category. In 1992, he undertook the production work with the Japanese pop-rock band Mr. Children on their debut album entitled "Everything". The producer and the band have gone on to record together to date, achieving mainstream success with cumulative sales of over 58 million copies albums and singles as of March 2013. In 1995, Kobayashi formed another multi-million selling pop group My Little Lover fronted by his then-girlfriend and first spouse Akko, and remained as a full-time member of the band until the couple's marriage broke up in the mid 2000s.