Oujougiwa no Imi wo Shire!

Ichimatsu Kairo (Aoki Yuzu) is an office worker who, while studying in college, was fond of cinema and even tried himself as a film director. Then, seven years ago, he met Kusakabe Hiyori (Mikami Ai), and invited her to act in his films, but the lovers' relationship lasted only a month, after which Hiyori suddenly disappeared.
Kairo was painfully going through a breakup, yearned for the girl, constantly reviewed the videos and photos with Hiyori, but one day a lightning strike burned down the house, and with it everything that evoked memories.
Completely desperate, the guy decides to commit suicide, but Hiyori suddenly calls him and asks him to become a sperm donor for her.
What is the real reason for Hiyori's desire to get pregnant?