Install those using Tampermonkey or a similar extension:
JPDB show all occurences – on JPDB vocabulary pages, shows the number of occurences in your decks of the current word
Add JPDB/Jiten/Kotobank links to jisho.org – on Jisho.org search result and vocabulary pages, adds links to corresponding entries in JPDB and Jiten, and links to search results in JPDB, Jiten and Kotobank
Add Epubs as new jpdb.io Decks – adds a functionality for importing epubs to JPDB (port of a Chrome extension by renjixd)
Hide Chinese Pixiv novels – when searching for Pixiv novels on Google, hide Chinese novels
Install those into the lua directory of your MPV installation