When starting a chain attack, each character starts with some number of TP. The amount is different for each character, and it's not clear what influences it. Knowing what changes this number could help ensure more powerful or consistent chain attacks.
The initial TP is always a set number during the first chain attack order under normal conditions:
Main character: Noah (30), Mio (25), Eunie (25), Taion (35), Lanz (15), and Sena (15)
Heros: Ethel (25), Valdi (20), Zeon (25), Teach (30), Riku & Manana (15), Gray (35), Isurd (40), Juniper (25), Ashera (15), Alexandria (30), Monica (30), Fiona (15), Triton (10), Ghondor (35), Cammuravi (15), Segiri (20)
Miyabi (15), Nia (15), Melia (35)
There are ways to increase the base TP for the characters, and this is can be done through various means:
Ways to increased the starting base
Equipping the Lost Vanguard skill Now That's Tactics can increase the base TP by 5 at rank 5, and then 7 at rank 10.
Equipping the Soul Hacker skill Deeply Tactical can increase the base TP by 5.
Equipping the Veneris Rings accessory can increase the base TP by 10.
Ways to increase the TP during chain orders
Teach's heroic chain bonus can increase all active characters base TP by 10, including the first chain order
Riku & Manana's heroic chain bonus can increase everyone's TP by 7
Miyabi's heroic chain bonus can increase Mio's TP, including the first chain order
I'm not sure if these are all of the conditions that apply, and I'll update as i find them Oct 19, 2022 at 14:02
I can't believe I didn't realize it was just fixed, but in retrospect, that must be correct. Poor Lanz and Sena just aren't tactical enough, I suppose!– TalOct 19, 2022 at 14:53
@Tal On the contrary, I would say it's even more tactical. I often start the chain order off with the lower TP attackers to ensure I don't go over 100% in a single attack, and save the higher TP values once I reach a higher chain order percentage Oct 19, 2022 at 15:13
Base TP is also fixed for each hero, not just the main six. (full list with spoilers) Oct 20, 2022 at 11:42