“Deleted Video” (削除動画, Sakujo Douga) was a short clip that Niconico would play in place of videos that were deleted or taken down, while still letting users comment and view the video's statistics. The feature would be formally retired around March 2020 after a website overhaul.¹⁾²⁾

The video would feature white text scrolling on a black background, read by a female narrator, with a rendition of either Hotaru no Hikari (蛍の光) or Sakura no Ume (桜ノ雨) by “Foo-san” (Fooさん). The thumbnail initially read “maybe it's been deleted?” (削除されたかも？), then it became “can't watch” (視聴できません) for much of its history, and last changed to a generic thumbnail in 2018 before it was discontinued.

Copyright claim.

Deleted by uploader.

Over the years, Niconico Douga users would make MAD videos, parodies, and remixes of these videos. One notable example was ".",³⁾⁴⁾ or “it's all your fault.” (全てあなたの所為です。, subete anata no sei desu.), which briefly inspired the "SubeAna-style" (すべあな風) trend. Aside from that, there's mostly just sentence mixing, and flute/recorder renditions deserving of a “Foo-san” (Fooさん) tag.

• If you're new to Japanese, the kanji being bigger than the hiragana and katakana is quite normal.
• Hotaru no Hikaru is a Japanese song, commonly associated with graduations or store closings.
  • The song is inspired by the Scottish song, Auld Lang Syne, so English speakers unaware of the phenomenon might end up hearing the “should old acquaintance be forgot” lyric instead.
  • I was always given Sakura no Ume, so I have no attachment to the Hotaru no Hikaru version.
• Unfortunately, the video's discontinuation meant that it was now difficult to track which videos had over 100,000 or 1,000,000 views, unless you look for the video's metadata on websites like Nicolog.

• Official Deleted Video on Niconico Encyclopedia
• @foo_san on Twitter