A secret message can be found on the title screen of the NES version of the game with the use of two controllers. At the title screen, select "CONSTRUCTION" on the menu. Press Start on Controller 1 to enter the mode, then press it again to return back to the title screen. Repeat this seven times. After the seventh enter-and-exit, hold Down on Controller 1 and press A eight times on Controller 2. Then, hold Right on Controller 1 and press B twelve times on Controller 2. Finally, press Start on Controller 1 to activate the message featuring an animation of a green droplet falling.

"THIS PROGRAM WAS
WRITTEN BY
OPEN-REACH
WHO LOVES NORIKO
....."

The most likely person as to the identity of "Open-Reach" is Tomcat System's founder and programmer Ryoichi Ookubo because of the similarities between "Reach" and "Ryoichi". It should be also noted that his name is hidden twice in the game's ROM, and from one fact pointed out by a Russian LiveJournal user, that the name Open-Reach appears as "OPR" on the title screen of another game Tomcat System developed, the 1991 Famicom game Castle Quest published by Hudson Soft.

As for Noriko, her identity remains unknown. In the comments section of the sourced video, one commenter claimed that Noriko was Ookubo's daughter who was three years old at the time of the game's development, while the aforementioned LiveJournal user claimed that Noriko was a romantic partner, claiming her to be a former Namco graphic designer named Noriko Ikegawa (whose name would later appear in the credits for the Nintendo game Animal Crossing as a model designer), but there is no substantial evidence to support either of these claims.
Contributed by MehDeletingLater
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