It's a port of Kirikiri which is a rather popular engine for visual novels in Japan. There's about a 1/2 chance any given VN is implemented on Kirikiri - this allows to run a sizeable chunk of them on the switch (with some compatibility hacks applied, depending on the game.)
Version 1.1.0 of Kirikiri for Nintendo Switch / ニンテンドースイッチ用の吉里吉里
Changes in this version:
Higher quality icon
Font system from krkrz dev_multi_platform branch is implemented