The author's really dedicated to this couple, huh? I respect it, I respect it a lot!
As of right now, the author's currently serializing
Isshiki-san wa Koi wo shiritai, which seems to be an alternate story featuring these same two characters. As in the only difference I noticed between the characters in Ms. Rinna's Lovesickness and that of the new work is that Meishi's last name is slightly different. (Like I said, the author's
really dedicated). Still, the story between the two of them is different, as there the two enter a secret relationship as opposed to RInna not knowing what love is in the original.
However, the new work was serialized this year, while Ms. Rinna's Lovesickness's ended on December 2017. n the gap between these events (December 2017 - December 2019), the author published 17 doujinshi featuring the main couple. 15 main chapters, and 2 .5 chapters that seem to feature them with another character. The majority, if not outright all of them, seemingly focus on the events that occur with the two main leads as a couple. They all look REALLY wholesome, to be honest - some being lewder than others, hence the Ecchi tag.
Taking all of this into consideration, as well as the author stating that "You can also enjoy these by themselves. If you combine it with the commercial book, you can enjoy them even more!", I think that this can be viewed as essentially a sequel manga of sorts.
