Hello, Good-bye (ハローグッドバイ, Harō Guddobai) is a Japanese adult visual novel developed and published by Lump of Sugar.

The story resolves around the protagonist, Kaito Toubu, a secret agent tasked with infiltrating the demilitarised territory of Morino in an alternate universe Japan.

There are four main plot lines that the player will have the chance to experience, one for each of the four heroines: May Yukishiro, Suguri Saotome, Natsume Rindo and Koharu Hiiragi.

Once the player has accomplished all the tasks or completed the routes, they will receive the privilege of having a glossary of terms from the game and their definitions, background CG and music libraries, a sprite viewer and even an additional minigame starring the Lump of Sugar mascot, Azrael.

[16] The fan book contains a terminology dictionary, story and character introductions, interviews, autographs, an illustration gallery, comments from staff, and a short four-panel manga titled Lump of Comic: HGB, which can also be read online.

Marine Entertainment released a spin-off drama CD titled To You the Commonplace Miracle (ありふれた奇跡をあなたへ, Arifureta Kiseki o Anata e) on August 12, 2011 written by Lump of Sugar.

[20] The opening theme for Hello, Good-bye is "Goodbye Crisis" (グッバイ クライシス, Gubbai Kuraishisu) by Masami Okui,[21] with lyrics written by Trinity, and arrangement by Macaroni☆.

The ending theme "Unnamed Place" (無名ぷれす, Mumei Puresu) is by Haruka Shimotsuki, with lyrics by Mao Sumita.

[27] There are also collectible Lump of Sugar trading cards that depict the characters from their existing visual novels, including Hello, Good-bye.

[33] Moe Game Award gave Hello, Good-bye silver (second place) for the best visual novel song in 2011, which was "Goodbye Crisis" sung by Masami Okui, losing only to Grisaia no Kajitsu which achieved gold.

[35] On reviewing the English-language version, Thomas Knight of NookGaming praised the artwork, and enjoyed all of the routes, but criticized how quickly the relationships with the heroines developed.