Insect trainer location : Butterfly Estate, just at the right of the gourds behind a mansion/house. (You can find the Butterfly Estate by accepting the quest from the girl NPC, asking you to deliver flowers to a friend. otherwise it is just beyond Rengoku Village.)
Insect Breathing has 4 moves; Bee Dance; Butterfly Dance; Centipede Dance; Dragonfly Dance.
1st form: Bee Dance, a single jab sending you slightly forward, filling up 1/6 of your poison bar. (Close ranged)
2nd form: Butterfly Dance, dash forward and stab your foe dealing little to decent damage, filling up 1/6 of your poison bar. (Ranged)
3rd form: Centipede Dance, applies automated poison to your enemy while dealing little to decent damage. (Combo)
4th form: Dragonfly Dance, stab your foe 3 times, fills your poison bar dramatically, and deals decent to high damage. (Close Ranged)
Insect Breathing users now possess a "poison bar", when filled up your character deals poison damage (ticks) to your enemy.
Moves that fill up the poison bar are : 1st form : Bee Dance, 2nd form : Butterfly Dance, and 4th form Dragonfly Dance. (3rd form Centipede Dance does not fill up your poison bar, however it does apply poison to your enemy by default.)
Insect Breathing has been reworked, information is up to date as of 2022/12/27.