After buying and playing on a standard 13 string koto, I knew I wanted a bass koto as well. The bass koto was everything I expected and more. It's taller (about 1 foot or 30cm longer), wider, and deeper than a standard koto. The strings are thicker as well, requiring a little more effort to position the ji and strike the strings, but the sound produced is well worth the effort. The strings are also yellow, which gives the bass koto an even more distinct appearance.
Compared to the bright, shimmering sound of a standard koto, the bass koto has a deeper and richer tone with a fuller, more resonant quality. The two played together make an even more impressive sound, complimenting each other beautifully.
My base koto came with a carrying case, a cover, a stand (which is the right height for playing in seiza position), and a tuning wrench.
Overall, I'm very happy with my new bass koto, and see myself playing it on a regular basis going forward!