Kishin Houkou Demonbane (TV)

Noir-Style Setting, mechas fighting and protagonist doing detective-y work. 

Both have the same boy-girl magical pact sealed by a kiss. 

Both have giant robots that are godlike by the end of the series. 

the main protoganist is pushed around by this wealthy girl with lots of maid.  

Similar type of protagonist and heroine pairing  

Both series contain a dark theme and background. Additionally, both series' main protagonists lives are changed forever when they meet a mysterious girl who grants them a power in the pilot episode. Both series also elements of action, drama, comedy, mecha, and later romance. 

Fantasy. And as I started watching to Dantalian, it remembered me of Demonbane, because both of them are involving the theme of grimories. 

Nun loli Index-tan has forbidden knowledge contained in "103,000" magic grimoires. Loli character Al Azif from Demonbane is a book. Literally. Oh and there's also magic in both and lots of pew pew. 

Magic, big enemies, stupid plot, arrogant lead character and a love plot. Both have that. 

Both are mecha and have a girl that fights together with the main guy.  

Both have a boy-girl pact in order to develop hidden battle skills 

Both Series has a Strange Girl that Control's the Robot while Asura Cryin has a Ghost Girl and Demon Bane has a Magic Girl which transform into a Book. They Quite really Similar, A Girl which is the Core of the Robot while the Main Guy give's the Command. 

This two animes are similar in many ways, both main character have a contract between Yurine from Karas and Azif Al from Demonbane which give powers when they stay togheter. There is a evil organization in both anime who want to destroy the town or world and the ending is almost same.