User blog comment:Skeith9/Heroic Spirits Speculation/@comment-5739199-20140507023222/@comment-24762556-20140509175616

The name of the manga you're looking for is "Sei Onii-san" or or in its official eng name "Saint Young Men"

Modern Japan's attitude towards religion is really iffy, they believe in whatever aspect of religion they want to believe. The majority of Japanese will write down Shinto or Buddhism when asked about their religion, but they hardly participate in any (non-holiday) religious ceremonies apart from weddings and funerals.

They may want to believe in a single supreme capital G God, or they may want to believe that multiple gods exists, or they may not believe in any supreme beings at all, that's why you often see anime characters ask each other "do you believe in God(s)?" rather than "what religion are you?". Atheism isn't a big deal, no one's going to point fingers at each other for what you belive or don't believe in like you would see in some other countries.

Other religious activities such as praying at Shinto shrines are more considered as part of the Japanese culture itself more than a strict guideline dictating worship, that's why it allows for mix-and-match beliefs for anyone to suit themselves with, such as how Japanese girls often hesitate whether they want to have their wedding set in a church or a shrine, it's not a matter of beliefs, it's a matter of preferences.