MKON-102 My beloved girlfriend was brainwashed by the cult leader and fell to become an exclusive internal ejaculation toilet for believers

I went to the house of my new girlfriend, 'Kana-chan,' for the first time. There was a large photo of the cult leader in the living room, and I was informed that everyone in her family except Kana-chan was a fervent believer. Of course, such things don't change how I feel about Kana-chan. As we were starting to get into a good mood, Kana-chan's older brother came home. 'We're going to perform an important ring ceremony now, so sorry, but could you go home today?' I have no intention of interfering with their family beliefs, so I'll go home for today. But what is this 'ring ceremony'? I feel a sense of unease...