Starting in Honkai impact but why did I reincarnated as a slime hollow

When our main character mysteriously finds himself transported into the world of Honkai, without a single knowledge about it. he didn't even notice that his journey begins in the Siberia at the Cocolia Orphanage. And created a strong bound with Bronya and Seele. To help Seele and Bronya he accepted Cocolia proposal to control the quantum energy and get stronger and gather more data for the expirement to get safety. But instead he got reincarnated as a hollow in bleach as a slime and with Rimuru skills.