Each is about a boy who is killed. He is given some difficulties by a supernatural being (the Undertaker or Shinigami), who later saves his life....but in exchange, he must work for them.
Have a similar, slightly over-the-top style.
Both Sougiya Ridoru and Shinigami Doggy involve younger boys who get involved in a contract with young men in order to achieve a goal. They both deal with similar topics (undertakers and shinigami) and have slightly dark atmospheres. Also, some of the characters act the same at certain times (Shin's actions towards Ren are sometimes like Riddle's actions towards Hayato).
a relatively normalish-teenager runs in with a demon(MTNN)/shinigami(Shinigami doggy) both are hilarious and funny and in so reminded me of each other. While in Shinigami doggy the boy has to work with the shinigami to save his life, the girl in MTNN makes a deal with a devil to save her father and from that they are both dragged into a situation that is more than they bargained for
both run into a creepy [old-young] guy and begin to experience a series of phenomenon of evil spirits, both boys then end up joining previously said creepy [old-young] guy and begin fighting for the sake of their own existence
if you like one you'll like the other >_<
Both the Shinigami, Shin, and the wizard, Tarnia, take in the main characters after they die and have them become their servants. Both boy characters do not have much of a choice and are somewhat indebted to their saviors. However, Shinigami Doggy has more of a Shounen Ai element to it.