After graduating from the Applied Chemistry program at Sophia University Graduate School, Yamashita joined Ricoh Co., Ltd. in 2009. He was involved in next-generation toner development and new material development. In 2014, he transferred to the new business development department and led startup investment and collaboration projects, as well as launching the bed sensor system business. In 2018, he joined KDDI Corporation and was involved in launching 5G services. Subsequently, he was responsible for startup investments and new business development. In 2022, he joined the CVC team at SEKISUI CHEMICAL to oversee startup investments for new business creation. He has been stationed in Silicon Valley since July 2024.