The answer of the tenth riddle - The Return of Long Lost Promise

The first line "The riddle of childhood was discovered"

» The riddle from the past when someone was still in their childhood."

The second line "Helped him remembered"

» Made 'him' remembered something.

The third line "A certain promise"

» He remembered a promise when he saw the riddle.

The fourth line "To the meeting at the place of memories"

» The promise was to meet someone at someplace.

The fifth line "The clue was animals"

» This referred to the said riddle, it seemed to be some kind of puzzle or code, which the clue to solved it was 'animals'.

The sixth line "That what it said"

» Line above was mentioned in the riddle.

The seventh line "He tried, but couldn't solved it, he afraid"

» 'He' couldn't solve the riddle.

The eighth line "Wondered she would still waiting for him all this time"

» 'She' probably the one he would meet at the 'place'.

The ninth line "Finally, the sounds was the answer"

» He finally knew the answer of the riddle, and it was a 'sound'.

The tenth line "We met, but she said she wasn't the one"

» 'We' (must included 'him', possibly he had a company with him at the time) met 'her', but then 'she' said she wasn't the person who he was looking for.

The eleventh line "Though he could still recognized"

» But he did recognized her that she's the one.

The twelfth line "That beautiful hair of hers"

» Her hair was what made him remembered her. Easy to distinguish from normal hair most people had.

The thirteenth line "The next time would be sooner"

» This probably meant the meeting of them, that would be sooner next time.

The fourteenth line "Definitely..."

» The affirmation of the thirteenth line...

If 'He' was Agasa, and 'she' was Fusae Campbell-san, everything would all came to you mind...

The riddle was the code she gave him 40 years ago, telling the location where they would meet again in every 10 years : 4163 33 6 0, under the number was "The hint is: animal".

Agasa and Detective Boys (the company) ended up at the zoo when they were solving the code. Conan figured that the numbers were actually, the sound of animals pronounced in English.

4163 was "Cock-a-doodle-doo" of a rooster, referred to the elementary school. 33 was "Bow-wow" of a dog at Noi-san's house. 6 was "squeak" of a mouse (hamster, in this case) at Chouno-san's house (Trans-gendered old friend of Agasa, now a female) And 0 was nothing, meant "no animal" which referred to her house which had no animal.

When you say all the place in order...

Japanese - Shogakkou Noi Chouno Kinoshita

English - Under the elementary school's gingko trees.

They found her at 'the place', but she mistook the Detective Boys as 'Agasa's grandchildren' (and Conan's flashback of her and Ran.) and didn't tell him who she was. Though he remembered her and shouted that "he's still love the gingko leaves, even now" She asked Billy (friend of Fusae) to take her there again in the next ten years, but he assured that it would be sooner than that...

The next riddle's out! Check it! XD