They both hung up smiling. Not because it was funny. Because they finally understood: some nights don’t end. They just change shape, carried inside you like a portable fire, warm and destructive.
Since there is no official "portable" version (like a dedicated handheld console game for Nintendo Switch or PlayStation), "portable" in this context usually refers to accessing the manga or related media via mobile devices. How to Access the Manga on Portable Devices fuufu koukan modorenai yoru manga portable
It seems you're asking for a deep narrative inspired by the phrase (夫婦交換 戻れない夜), a known adult manga series about couples engaging in a spouse-swapping ritual that irreversibly changes their relationships. The word "portable" suggests a version that could be carried, adapted, or played out in different settings. They both hung up smiling