Troop HP: increase
Troop DEF: increase
Troop ATK: increase
Tomoyo looks meek but don’t let her appearance fool you. She deals a lot of damage to all foes simultaneously. Bloody Charge-up allows her to heal herself as well. In those campaign and special events where you are only allowed to use a specific color hero, her Avid Rampage can be of some benefit as for 6 rounds it restores 5% Rage per round for all purple heroes.
But more importantly, she is another hero whose troop skills increase all troop bonuses. So she should definitely be upgraded to 131.