Here's the dictionary:
(last updated: 2023-01-24)
After installation, you will have a new item in your Kobo's dictionary drop-down menu called "日本語 - English (Custom)". Select it to use this dictionary.
The dictionary entries look roughly like this (but with nicer rendering on the Kobo):
The entry header (at the top) consists of four parts in this order:
After the entry header is a numbered list of definitions/translations, generally with more common usages closer to the top.
If you select a single kanji character, there will also be a kanji entry, which is a bit different from a word entry. Kanji entries look like this:
The header shows an enlarged view of the kanji and a list of (rough) associated meanings. The katakana entries (separated by slashes) are the onyomi readings, and the hiragana entires (also separated by slashes) are the kunyomi readings.
Despite having an English->Japanese dictionary, the Kobo line of e-readers do not have an official Japanese->English dictionary available. Moreover, although there are some unofficial dictionaries floating around online, they seem to be hacked together based on shoehorning English definitions into the Kobo's official Japanese-Japanese dictionary. Although that approach works to an extent, it also results in a dictionary with clear limitations and a hacked-together feeling.
I wanted a clean Japanese-English dictionary on the Kobo, generated from scratch, that functions well out-of-the-box. So I made one. The result is the linked file at the top of this page.
The word definitions, name data, and kanji data are from the JMdict, JMnedict, and Kanjidic projects, respectively, all of which can be found here:
The pitch accent data is from here:
Short answer: it's not perfect, but it should work in most cases, yes.
Long answer: the displayed entries will always be in dictionary form, but the search index also includes basic conjugated forms to help find the right entries when you highlight words. Nevertheless, Kobo's dictionary search algorithm seems to occasionally fail at finding the right entries anyway. But most of the time it works.
Also, because of the duplicated entries for conjugations, Kobo will occasionally display duplicate entries when using this dictionary. But this is rare.
Although I've tested this on my own Kobo e-reader, and it seems to work well for my own personal usage, I cannot and do not make any guarantees about its fitness for use. In other words, use at your own risk.