During the development stage of the business idea for Brightstorm, Kim met Marshall and Walsh through KTB and the three co-founded Brightstorm for which KTB led a Series A investment. From the launch of its online services in 2008 until August 2009, the course model of its content was subject-oriented. Bumsoo Kim, then investment principal at KTB Ventures, had interests in investing in a K-12 online education company as a result of the unfulfilled potential he perceived within the industry at the time.

At this time, Brightstorm adopted a freemium business model which offered free content in math and science and paid content in test prep for SAT, ACT, and Advanced Placement tests. Kim is originally from South Korea where college entrance is hyper-competitive and, thanks to the country’s early adoption of nationwide high-speed internet, has had many successful online education services. Study videos cover math courses ranging from pre-algebra to calculus as well as English, science, and test prep for SAT, ACT, and Advanced Placement tests. Brightstorm is targeted towards teenagers to help improve their grades through leaning exercises and SAT prep. College Counseling provides answers to academic questions commonly asked by high school students and their parents.The majority of Brightstorm teachers possess master's degrees or PhDs from widely recognized universities.

It is reported that Brightstorm has delivered over 20 million lessons to more than 240,000 registered users from over 200 countries.

In September 2009, Brightstorm launched its “free math help” section which contained more the 2,500 math videos across 6 math subjects. In July 2012, Brightstorm changed to an all-you-can-eat business model where users need a monthly subscription to watch all videos offered on the site. Brightstorm is an advocate and example of flipped classroom teaching where students can learn on their own through online videos. We combine time-saving HD videos with tools like textbook video locator for a comprehensive learning experience.

Users may ask up to three math problems per month and are guaranteed to receive solutions within 48 hours.It features thousands of study videos as well as other study tools and resources such as Math Genie and College Counseling.