I apologize for taking so long to clarify, I only saw the reply today. Under variants, there's one named "Shunbun" which mentions ume shiso. Thank you!

I am guessing based on Simon's results specifying a liquid, its probably referring not to a garnish of ume and shiso[also called perilla], but to a product like Umeshu[plum wine] brand Choya Umeshu Shiso. They also produce a Choya Umeshu Honey, which appears to be the product the "Risshun" refers to.