「Ejaculation of hedgehogs」describes succinctly the general human male and human female relationship with regard to: CHANCE, FATED ROMANTIC TIES, DESTINY, KARMA, and in detail the MALE-FEMALE BONDING AND RELATIONSHIP IN MARRIAGE, the PERSONAL CONNECTION TO A SPOUSE, and the ultimate AFFINITY that a husband and wife have for one another. In the quote below, it is recommended when reading this a second time to swap the term 'hedgehog' for 'human beings in nightclubs and bars' in your mind in order to clearly understand the intention of the sages:
「The ritual seems more like a fight as it is an extremely noisy event. [it sounds as if people are screaming at the top of their lungs] The courtship, or 'pre-mating display,' is initiated by the male when he comes across a solitary female on his nightly wanderings. He approaches her, snuffling and snorting, and circles closely round and round, trying to claim her attention. The female shows no interest. She twitches violently and repeatedly turns away from him. The male persists and circles closer, snorting louder and louder, sometimes for hours. Often a second male will approach, attracted by the noise, but the intruder's presence is not tolerated, and the male inserts his muzzle underneath him and pushes him out of the way. The female, totally unconcerned, may wander off. A high proportion of attempted hedgehog matings fail due to the female's lack of interest. Ultimately, however, the female may become receptive and allow the male to mount her. Mating may only last a minute or two, and then the pair separate. The male plays no further part in bringing up the family, and if the hedgehogs ever meet again, it is probably only out of chance. Unless the female places herself in the correct position, mating will be impossible. She must lie with her hind legs spread out, belly pressed flat to the ground and nose pointing upwards. The formerly aggressive spines must be laid flat: the skin of a male hedgehog's belly is thin, and he could be badly injured. He mates with her from behind, gripping the spines with his teeth. Hedgehog reproduction is not very efficient. The female often mates several times before becoming pregnant, and quite a few females may reach the end of the season without conceiving.」
[ now-dead link was https://www.hedghogz.co.uk/hedgehogs/babies.php 2012-08-27 so instead see https://www.wildlifeonline.me.uk/animals/article/european-hedgehog-breeding-biology-season-courtship 2023-05-17 ]
「Threads like porcupine, hedgehog.」Hedgehogs mostly prefer, have an AFFINITY, for copulating and foraging in hedges (surprised?) that often line the EDGES of a field, the hedge being the BORDER or SEAM that CONNECTS two fields. The FRINGES or EDGES of a cloth may also be frayed or unfinished with many protruding individual threads, that resemble, in a way, a porcupine or hedgehog.

External source definitions …excluding politically incorrect concepts and other meanings deemed offensive today; may include extended definitions, euphemisms, and mnemonics)
Chinese: Japanese variant of 緣|缘
Japanese EDRDG: affinity, relation, connection, edge, border, verge, brink
Unihan extended: hem