The general meaning of "from now on is spring and autumn, and wind and moon are not related" means that from now on, he will live in seclusion in the mountains and forests and not care about worldly affairs.
"Spring and Autumn" refers to the quiet and peaceful place where Onmyoji retreats. It is a romantic place where cherry blossoms are scattered all year round and the water is like a mirror. It is a space where onmyojis can play the piano, drink tea, appreciate flowers, enjoy life, and meet lovers privately.
"Fengyue" Fengyue means cool breeze and bright moon, and also refers to sensual and erotic places, coquettishness and amorous feelings. The words come from Han Wu's "Fu of Mrs. Li": When I moved to the clouds, Pei returned to the wind and moon. Tang Dynasty's "Gift to the King Judge, Shi Yu returned to seclusion, and lived in Lushan Mountain with a folding screen": The wind and moon were good in Kuaiji, but he went back around the Shan River. Clouds, mountains and seas emerge, and figures appear in the mirror.
Extended information:
The poems about "returning to seclusion" are:
1. White hair should go back to seclusion, and green mountains can build huts. ——Song Dynasty. Lu You's "Thinking of Shu"
Translation: A man with white hair should live in seclusion in the mountains and forests, and live in a hut in the green mountains.
2. What happened to Nuo Nuo Ping? Lao Huangguan retired to Jinghu Lake. ——Song Dynasty. Lu You's "Ti Zhaibi"
Translation: There are many disturbing people and things in life, which come and go without stopping.
3. The clear stream is unfathomable, and there are only solitary clouds in the hidden place. ——Tang Dynasty. Chang Jian's "King Su Changling Resides in Seclusion"
Translation: The water in Qingxi River is unfathomable, and only a white cloud can be seen in the seclusion place.
4. Beans are planted at the foot of the southern mountain. The grass is full of bean seedlings. ——Tao Yuanming of the Jin and Song Dynasties, "Returning to the Garden and Living in the Fields·Part 3"
Translation: I am planting beans at the foot of the Nanshan Mountains, and the weeds are lush and the bean seedlings are sparse.
5. In Shuiyun Village, the dust from cars cannot reach the door. ——Tang Dynasty. Wang Wei's "Mountain Dwelling in the Dark Autumn"
Translation: The fragrance of spring may as well be allowed to fade away, but the kings and grandsons of the mountains in autumn can stay for a long time.
Reference materials: Baidu Encyclopedia - Spring and Autumn are not in contact with each other
Reference materials: Baidu Encyclopedia - Fengyue