Kobayashi made her debut in the Continental Cup on March 8, 2008 in Zaō and finished in 29th place. In the second competition she was able to get points again as 30th. Kobayashi has only competed internationally in jumping in Japan. The 2008/09 season was their most successful to date. She started again in Zao and finished 26th and 25th. In the 2009/10 season Kobayashi won a point in the first competition as 30th, but missed the second round in the second competition as 32nd. In the 2010/11 season she picked up a point as 30th in Zao.
On March 3, 2012 Kobayashi made her debut in Zaō in the ski jumping World Cup . With a 40th and a 41st place she remained without World Cup points. At the Junior World Championships in 2013 in Liberec , she was 24th in the individual competition, before jumping to fifth place with the team in the team competition. In January 2014 Kobayashi was used again in the World Cup, but was again without points. It wasn't until a year later that she finally succeeded with a 30th and a 23rd place in Sapporo . At the following Winter Universiade 2015 in Štrbské Pleso , she won two silver medals and the gold medal with the team in the second team competition.
At the 2017 Winter Universiade in Almaty , Kobayashi won the silver medal in the individual competition behind Haruka Iwasa and in front of Marta Křepelková . In the mixed competition she and her compatriot Max Koga won the bronze medal behind their compatriots Haruka Iwasa and Naoki Nakamura as well as the Czech team, while in the team competition with compatriot Haruka Iwasa she won gold before the Czech Republic and Russia.
↑ 小林 潤 志 郎 が 準 V 大 倉山 サ マ ー ジ ャ ン プ . (No longer available online.) In: Iwate Nippō WebNews. December 10, 2011, archived from the original on August 25, 2011 ; Retrieved December 10, 2011 (Japanese).