"Himawari wa Yoru ni Saku" (Sunflower ha Yoru) is a short OVA/visual-novel-style title often discussed among fans of romantic, character-driven anime with supernatural or slice-of-life elements. Below is a concise, shareable post you can use on social media, a forum, or a fan blog.
If you have any information about Himawari wa Yoru ni Saku, or believe you have seen this OVA, consider it the final lost petal of an unsolved anime mystery. himawari wa yoru ni saku ova sunflower ha yoru