Return is one of the four possible endings that can be achieved. Except for the last, every step must be done before defeating the Divine Dragon.
Step 1: stay loyal to Kuro*** Spoiler - click to reveal ***After obtaining the Stone, the Mortal Blade, the Flower and climbing to the top of the castle, you will encounter Owl. Choose "Break the Iron Code, stay loyal to Kuro" and defeat the Great Shinobi.
Step 2: eat rice*** Spoiler - click to reveal ***Travel to Inner Sanctum (Senpou Temple, Mt. Kongo) and request rice to the Divine Child. Eat it and use the Homeward Idol to return to the Dilapidated Temple and then return to the Inner Sanctum. Repeat this process until the Divine Child is sick and asks for a persimmon.
In case you don't have a persimmon, this can be bought for 30 sen from the Shugendo Memorial Mob (Mt. Kongo): from the idol turn left and walk through the wooden ledge.
Step 3: deliver*** Spoiler - click to reveal ***Once you've given a persimmon to the Divine Child, she'll give you Rice for Kuro. Travel to Kuro's Room and give it to him, rest at the nearest Sculptor's Idol and then talk to him again to receive Sweet Rice Ball. Eat it. Talk to the Divine Child again and then hand her Holy Chapter: Infested. This key item can be found at the bottom of the pond near the Temple Grounds (Mt. Kongo) idol (or, earlier in the game, can be received from the Main Hall Monk).
Step 4: get key items*** Spoiler - click to reveal ***After you've given Holy Chapter: Infested to the Divine Child, use the Homeward Idol to travel to the Dilapidated Temple and then return: the Divine Child should now be gone from her place (if not, exhaust all dialogue and repeat the process). Interact with the light beam in front of the temple to transport to Hall of Illusion and talk to her there.
After talking to her, get the following key items:
Holy Chapter: Dragon's Return:
Travel to Main Hall (Mt. Kongo), leave through the main door and turn right. Enter the cave and keep going until you find a mummy whose clothes are not as worn out as the rest. Give it to the Divine Child, rest at an idol and then get the next two items.
Fresh Serpent Viscera:
From Senpou Temple (Mt. Kongo) drop down until you find an Assassin (the small enemy with a hat) and use the Puppeteer ninjutsu technique on him. Keep going forward until you find a big tree near the broken bridge, climb it and grapple to the kite. This path will lead you to a cave with an idol inside and a wooden beam. Jump and perform a Plunging Deathblow on the Great Serpent to obtain the item and a trophy.
Dried Serpent Viscera:
From the Bodhisattva Valley (Sunken Valley), go opposite the Guardian Ape's place and enter the cave behind the Memorial Mob. Go deeper and jump left when you see the serpent's head. Use Puppeteer on the terrified monkey and grapple up when the serpent is distracted. The viscera is inside the building.
Step 5: receive Frozen Tears*** Spoiler - click to reveal ***Give both viscera to the Divine Child, rest, eavesdrop, rest again and talk to her to receive Frozen Tears (if the door remains shut, make sure Kuro has already cut himself with the Mortal Blade).
Step 6: give Frozen Tears to Kuro