Septentrion: Out of the Blue is a sequel to SOS released exclusively in Japan. Unlike the original game, the sequel takes place in a modern setting and doesn't have a time limit to finish the game, removing the sense of urgency.

The year is 1999, a sudden collision causes the luxury liner King Windsor to start sinking and players alternate between the ship's navigator Gerhard Brown and the chief engineer Carter to rescue each other and the passengers. The game tries to portray a naval accident realistically by having the ship tilt and making players follow safety precautions to avoid slipping and sliding to their deaths. Players navigate through the whole liner with the map hinting where to find the passengers while trying to uncover the truth about the accident. The survivors follow players around and the game keeps track of all the people players saved, altering the ending depending on the amount of survivors.