Kami nomi zo Shiru Sekai, Yahari Ore no Seishun Love Comedy wa Machigatteiru. Recommendations
Both are told from male perspective..
Both MCs are loners by choice ..
Both have many catchy phrases/ quotable dialogues ..
Both have some kind of philosophical/ psychological monologues ..
Both MCs are put in a situation where they have to go out of their ways and interact with others
Both series' male protagonists are class outcasts but due to certain circumstances, they must interact with those around them, often helping characters in their time of need. They are also intelligent & methodical thinkers, are often rather cold towards others, and prefer to remain in their own worlds. As a result, they can often be subjected to being mocked by other characters.
The shows are full of comedic gags and often parody the romance genre with the female protagonists behaving in ways completely different from what the male protagonists expect. Although there are romantic moments, they can often lead to comedic moments. All the male protagonist
They're both about loner high school kids and their love exploits. Both protagonists are cynical (though this manifests in different ways), both shows understand their characters well, both have harem elements (that are often subverted).
There is really nothing similar in the plot and little in the style, but hikkigaya and keima are essentially the same person. Both are total outcasts and cynics, but they prefer it that way. On occasion in both shows you begin to realize they both have a heart. Also, both shows have incredibly unsatisfying endings.