Shoumetsu Toshi

The same relationship that involves older guy with younger girl, were they have to go to such hardships in order to succeed.  

There’s really nothing similar about these anime. Settings and genres are very different. The only comparison I found was that both main heroines have a parent that they are trying to find. They don’t even know if they’re alive or dead. The missing parents of both characters left them a message that they were waiting for them in this place. Both anime are adventures leading to said place. Also, this place happens to be a very big hole in both anime’s. It’s up to a man/boy to take the woman/girl to the place where their parent is supposedly waiting for them.  

most of the themes are handled better here. 

Both shows are the lowest points MadHouse has done. 

Freelance MC who can do (almost) anything + girl who is searching for father. Also the plot revolves around a restricted area Ex. Lost or Dimension W. Also similar to Darker than Black for the same reasons.