This guide provided you with when I unlocked the memos of all the characters. They could possibly be unlocked in other time, but I haven't tried out yet.
在此只提供我解锁的时间段，并不一定唯一
A few notes:
'Before church' means right after you gained control of the characters and before starting the scenematics in the church (highly missable!). This means you should have them before you even get the character memo book!
有一部分的人物只能再去教堂前解锁，请务必小心



Charaters:
Nina, Mina: Twin daughter of Kites'. Usually in their house
人物：
妮娜 米娜： 凯特家双胞胎

Pipiro:
1,2: Unlock automatically after exiting the church at the very beginning
3: Unlock after talk to Mina before heading to church
皮皮洛：
1，2: 教堂上课完的剧情后自动解锁
3: 在去教堂前和米娜（凯特家的女儿之一）对话解锁

Pokkle:
1: Unlock after talking to Kite before heading to church
2: Talk to Nina after going to the shrine
3. Talk to Mina before heading to church
布库尔：
1 去教堂前和凯特对话解锁
2 触发神秘男子拿走雕像后和尼娜（对话解锁
3: 去教堂前和米娜对话解锁

Raspberry:
1. Unlock by talking to Effey before going to the church
2. Talk to Cherry after obtaining Idol of Earth
3. Talk to Eria after obtaining Idol of Dark

拉兹波利：
1 去教堂前和艾菲对话
2 拿到地之神像后和切利帕对话
3 拿到暗之神像后埃利亚对话

Pyotr:
1. 2: Unlock after talking to Pyotr before obtaining Idol of Earth
3: Unlock after talking to Pyotr after obtailing Idol of Dark

皮特尔:
1.2. 拿到地之神像前和皮特尔对话
3. 拿到暗之神像后和皮特尔对话

Peachem:
1 Seems to be unlocked when getting the keys from the Genomes
2. Talking to Miles, Wemick and Paul after the Water Idol (Credit to @snidne)
3. Unlocked after earthquake event (Credit to @snidne)

Kite:
1. Talk to Lucille after obtaining Idol of Water
2. Talk to Kite after obtaining Idol of Water
3. Talk to Chai after obtaining Idol of Fire

凯特：
1. 拿到水之神像后和琉希尔对话
2. 拿到水之神像后和凯特对话
3. 拿到火之神像后和库拉蒂对话

Lucille:
1. Talk to Lucille before going to church
2. Talk to Polly before going to church
3. Talk to Lucille after getting Idol of Wind

琉希尔：
1. 去教堂前跟琉希尔对话
2 .去教堂前跟波利对话
3.拿到风之神像后跟琉希尔对话

Nina/Mina:
1. Talk to Nina/Mina before going to church
2. Talk to Nina/Mina after obtaining Idol of Water
3. Talk to Nina/Mina after obtaining all six Idols

妮娜/米娜:
1. 去教堂前跟妮娜/米娜对话后得到。
2. 拿到水之神像后跟妮娜/米娜对话后得到。
3. 拿到六个神像后跟妮娜/米娜对话后得到。

Jiord:
1.Talk to Jiord after getting Idol of Earth
2.Talk to Jiord after getting Idol of Water
3.Talk to Jiord after getting Idol of Dark

Liesach:
1.Talk to Liesach before going to church
2.Talk to Liesach after getting Idol of Earth
3.Talk to Liesach after getting all 6 Idols

Wemick:
1. Talk to Wemick after going to church and before going to Shrine
2. Talk to Wemick after getting Idol of Fire
3. Talk to Wemick after getting all 6 Idols

Judith:
1. Talk to Judith after going to church and before going to Shrine
2. Talk to Judith after getting Idol of Water
3. Talk to Judith after getting Idol of Fire

丘特：
1. 拿到地之神像后跟丘特对话
2. 拿到水之神像后跟丘特对话
3. 拿到暗之神像后跟丘特对话

利萨赫：
1. 去教堂前跟利萨赫对话
2. 拿到地之神像后跟利萨赫对话
3. 拿到六个神像后跟利萨赫对话

威米克：
1.傍晚从教堂出来去圣坛前跟威米克对话
2. 拿到火之神像后跟威米克对话
3. 拿到六个神像后跟威米克对话

尤迪特：
1.傍晚从教堂出来去圣坛前跟埃利亚对话
2. 拿到水之神像后跟尤迪特对话
3. 拿到火之神像后跟尤迪特对话

Eriya:
1. Talk to Eriya after going to church and before going to Shrine
2. Talk to Eriya after getting Idol of Fire
3. Talk to Eriya after getting all 6 Idols

Polly:
1. Talk to Polly before going to church
2. Talk to Polly after getting Idol of Earth
3. Talk to Polly after getting Idol of Water (some said you need to use Pipiro to unlock)

Chai:
1. Talk to Eriya after getting Idol of Earth
2. Talk to Lucille before going to church
3. Talk to Chai after getting Idol of Wind

Apple:
1. Talk to Eriya after getting Idol of Earth
2. Talk to Apple after getting Idol of Earth
3. Talk to Eriya before going to church

Cherry:
1. Talk to Eriya after getting Idol of Earth
2. Talk to Cherry before going to church
3. Talk to Cherrya after getting Idol of Dark

Brick:
1. Talk to Brick after getting Idol of Earth
2. Talk to Effet after getting Idol of Water
3. Talk to Juno after getting all 6 Idols

Effet:
1. Talk to Polly before going to church
2. Talk to Juno after getting Idol of Fire
3. Talk to Effet after getting all 6 Idols

Juno:
1. Talk to Juno after going to church and before going to Shrine
2. Talk to Effet after getting Idol of Water
3. Talk to Juno after getting all 6 Idols

Makari:
1. Talk to Makari after getting Idol of Water
2. Talk to Chai after getting Idol of Fire
3. Talk to Makari after getting Idol of Light


Lainie:
1. Talk to Lainie after getting Idol of Earth
1. Talk to Lainie after getting Idol of Light
1. Talk to Lainie after plane crash


Pneuma:
1,2. Talk to Pneuma after getting Idol of Water
3. Talk to Pneuma after getting Idol of Dark


Plum:
1. Talk to Cherry after getting Idol of Earth
2. Talk to Plum after getting Idol of Dark
3. Talk to Plum after getting Idol of Light

Credit to @Jyral and @Wuffles for Cyrus memo3
Cyrus:

1. Obtained by talking to Pyotr after obtaining idol of the earth
2. Obtained by talking to Pyotr when he's in the idol room (I think it's after the obtaining the Dark Idol)
3. Obtained automatically after learning all 4 Arcanum (from him, not from books)

Philip:
1. Talk to Philip before going to the church (in the barn near the shrine; Thanks to @Roga de Ticon, you probably will need to talk to him more than once to unlock)
2. Talk to Philp after getting Idol of Water (in the maze)
3. Talk to Philp after getting Idol of Light (in the maze)

Paul:
1. Talk to Paul after getting Idol of Water
2. Talk to Paul after getting Idol of Fire
3. Talk to Paul after getting all 6 Idols

Ramsey:
1. Talk to Reginev (2nd floor of the pub) before going to the church
2. Talk to Ramsey after getting the Idol of Water
3. Talk to Ramsey after getting the Idol of Light

Reginev:
1. Talk to Reginev after the church and before going to the shrine (in the pub)
2. Talk to Reginev before getting the Idol of the Earth
3. Talk to Reginev after getting the Idol of Wind

Natalya:
1. Talk to Tom after the church and before going to the shrine (2nd floor of the pub)
2,3 automatically unlocked

Tom:
1. Talk to Tom after the church and before going to the shrine (2nd floor of the pub)
2,3 automatically unlocked

I thought it was automatically unlocked...I wasn't paying attention. Credit to @snidne for this one
1. Talking to him after the Plane Crash event unlocks his first memo
2. talking to him after obtaining the Water Idol unlocks his second memo
3. Obtained after having all 6 idols and obtained Infinite wings from him

Thanks for the help from @sidhe and @Jyral.
The English version is done, trying to get the Chinese version completed once I have the time. Advices are welcome and should you have any question, please let me know. Thanks for reading and sharing it.