Tomes: How Many to Grind

If my understanding is correct, to get a target Tome as a completion reward is the same as to pull a target character in gacha.

Among Tomes, Clauses, Treatises and others for Style Change are difficult to gather even if you exchange 2 of them with Tsubura* at the Nopaew Emporium.

Hypo Situation

• want 3 of Butterfly Warrior Clauses
• complete any Another Dungeon 4 times daily with 3 completion rewards
• chance of the Clause to appear: 0.1%

How Long It takes

This means you try 0.1% Lone Encounter gacha 12 times and the probability to get one or more of the Clause(s) is 1.19%.

Suppose 100 players want 3 of the Clauses. It requires 7 and a half months (2,674 / 12 / 30) for a half of them to achieve their goals.

Nonetheless, JP ver. 2.0 introduced a new Another Dungeon where completion reward slots increased to 5**. If the probability of appearance is the same, time to be required will be reduced to around 3 and a half months.

Moreover, since there will be more than 10 AS characters available and you will have more chances to obtain some of the AS Tomes, mental stress will be somewhat relieved.

*Tsubura means like being round and lovely.
**Light/Shadow points needed to obtain the rewards are 24, 60, 120, 240 and 360.