Seccom Masada-sensei (or Masada) is a character found in Madotsuki's dreams. He is popular with fans. He is found by sleeping in any one of a number of beds found in the dream world, going down the staircase, walking past the elevator, and using either the Umbrella or Yuki-onna effect to extinguish the fire.
His name is Sentimental Komuro Michael Sakamoto Dada-sensei (センチメンタル小室マイケル坂本だだ先生). Obviously quite a mouthful to pronounce, fans shortened it to Seccom Masada-sensei (the letter c being doubled probably to avoid trademark infringement of a security company of same name, which is famous in Japan). He is found in a black-and-white spaceship, apparently the pilot. He stands next to a piano. The player is able to "speak" to him, yielding a beeping noise that some Mario players may find familiar. Masada is the only character who walks backwards in the game, although the only way to see him walk is by activating the Knife effect.
Masada Seccom has not really been involved in major plots, aside from being the back up priest at Splashwoman and Quickman's wedding. Masada was also granted a cameo in A Sheezy Christmas Carol, where chases around David Sledge Brother after David and Jojora landed in Metanezer Scrooge's childhood neighborhood. Otherwise, he mostly just hangs around, making screeching NRRRRRRRRRRRRRRN noises and cracking his neck.