I haven't heard about the story of Shantanu and Puchki before. It might be a very specific or regional story. Maybe it's from a particular book, movie or a local folktale. Without more context, it's difficult to tell the full story.
Since I'm not familiar with the Shantanu and Puchki story, it could be a story created within a certain community, family or by an individual author. It might be about their relationship, their adventures or some important events in their lives. But without any prior knowledge, I can't really tell the full story.
I'm sorry, but I don't know the specific story of Shantanu and Puchki. There could be many fictional or personal stories with these names.