"And to the Door of the Kingdom…"
Shortly after the end of episode six, Rin wakes up in Eipos' castle at the foot of Yggdrasil, the mythical tree that generates time spores, since Eipos let her regenerate instead of consuming her spore. She is then locked in a room with a masked angel and kills him, only to discover that it was Ihika. Meanwhile, Mimi and Mishio desperately search for Rin and learn the location of Eipos' castle from the informant. Tajimamori, former Guardian of Yggdrassil, invites them to his castle, explains that his son Eipos aims to become the new eternal Guardian, and opens a portal to Eipos' castle for them. There, Rin is losing the battle against Laura but Eipos double-crosses her and Rin escapes. In retaliation, Laura teams up with Mimi and Mishio and leads them to Yggdrassil. Rin is already there and meets Tajimamori, her millenia-old love. They have sex until Eipos arrives, kills his father, and pushes Rin into Yggdrassil. Mishio arrives and tries pulling Rin out. She fails but Rin manages to grab Kōki's time spore that she found in the sea after episode four and Mishio brought along with her. As Yggdrassil tries to merge with her, Rin consumes Kōki's spore and his spirit helps her to break free. Mishio, Tajimamori's descendant, pulls Rin out and back to the castle. Eipos attacks but Rin reveals that she became the new Guardian of Yggdrassil and pushes Eipos into it himself. Before he is consumed, she feeds Tajimamori and Laura's spores to him.
In the epilogue, Rin gives birth to Tajimamori's son and continues living in Eipos' castle with Mimi and Mishio. Her closing narration reveals that their son is linked to the Yggdrassil and this link will spread throughout mankind with his descendants.

How they just have sex and make love there lol.
It's amazing how an angel is not male nor female.
And their madd stong, but damn Rin became stronger then Eipos ever was.