>>2859761"The number of my (best?) 劣等上等 Nico video, including sm."
Since the hint truncates elongated vowels (ou), the advice to type it out would not be very useful here without basic Japanese knowledge, but if you see such strange-looking words, the first thing to do is to try typing it out somewhere like Google Translate with kana input enabled. Maybe some advanced IME software would be able to figure out which word you want though.
How to find it:
0. Try googling the username along with "nicovideo." In this case, you will likely fail to find anything useful for some reason, so this step can be skipped.
1. Go to the user's bowlroll page.
2. Click the Twitter icon by the avatar.
3. Look for any links that could point to his account, starting with the bio. Lit.link is used for link collections, so click there first.
4. Nice, there's his Nico account link. Now click it.
5. It conveniently directs you to his video list, so all you have left is to search for a matching video name and copy its number to the password input field.
6. ???
7. PROFIT!!111