I’ve been reading a lot of Japanese green tea sites (in Japanese) and it seems to be common knowledge that buds have the highest concentration of caffeine. There is also a bud tea in Japan, mecha. Interestingly enough it’s not considered to be as good as gyokuro or high-grade sencha, even though the cultivation process is the same. The exact opposite of Chinese white tea, where it’s considered to be of highest quality.
A Digital Ocean of Tea