Walking While Talking
Explanation
Walking While Talking (aka WWT) is a state where time continues to advance, possibly with the ability to control Ammy, while dialogue is up. WWT is normally activated by triggering dialogue and interrupting it with a cutscene. Only certain combinations of cutscene and dialogue will produce this state -- this, along with the effects of WWT, is not fully understood. There are two distinct kinds of WWT state -- one allows full control of Ammy; the second allows pausing and the use of the brush and allows time to move, but does not allow for control of Ammy without "breaking free" via triggering another cutscene.
With WWT activated, speaking to an NPC will generally replace the existing dialogue while Ammy retains WWT. On most versions of the game, if one has the dialogue of a character with a portrait on the screen and then moves too far from that character, the game will crash. This presumably occurs because character portraits only remain loaded when Ammy is close enough to an NPC. This crash will even occur if it is Issun's dialogue on-screen. The Wii version has more lenient crash behavior -- instead the character's portrait may be replaced by some other graphic, such as the Stray Bead icon, and in many cases it is possible to move far away from the NPC without a crash. What determines crashes and portrait replacement on Wii is not well-understood.
WWT can be cancelled by simply closing the dialogue box. It is also cancelled when going through loading zones (long or short), meaning WWT must be activated in the same map where it is used.
WWT is not speedrun-applicable, but may become so in future if its current limitations are overcome.
Areas where WWT can be Activated
Kamiki
Unlike most cutscenes in the game, Ammy is not prevented from drowning after Rejuvenating Kushi's waterwheel. By jumping into the river near Kushi and waiting until Ammy is just about to drown before using Rejuvenation, one can respawn before the scroll transition occurs and tackle Kushi. See https://youtu.be/Dl9lI99ih88. If one then allows the cutscenes to play out in the correct sequence, one can exit the dialogue while Kushi's introductory text stays on screen.
If the dialogue is taken to Komuso, you can start his battle from outside the battle barrier, allowing you to effectively flee the battle, though there are no directly interesting consequences of this.
Shinshu
DriftingPancake/ZLAMP reported that they performed WWT in Shinshu using Issun's intro text for the dojo, possibly via some effect of the Invisible Cherry Bomb Glitch, but could not replicate it.
Agata
It is possible to delay activation of the cutscene which plays when one of the spherical objects in the area is returned to Sleepy (aka Nemui, the bear). This is done by cutting a torch, then pushing the ball into position so that the torch will push it into Sleepy's trigger when the torch respawns. Before this happens, you can jump down and go into the cave below, then PS the chest by the guardian sapling to collect the Prayer Beads. The associated tutorial cutscene will be interrupted by the Sleepy cutscene. Ammy will then be placed in a state that isn't controllable, but allows day-time to pass. If one waits for a day-night transition and cancels it by skipping the Sleepy cutscene, another state is activated where the day-night transition will interrupt the next NPC dialogue triggered, giving WWT. See https://youtu.be/r_3xO4vZSaU.
This WWT has a unique use: if one begins the dialogue for fishing with Kokari, then feeds an animal as the transition to fishing occurs, the minigame will immediately end after the introductory dialogue. When loading completes, all NPC's will T-pose and Ammy will have a strange sort of no-clip.
During this no-clip, Ammy isn't affected by gravity. If she jumps, she gains no height and will get stuck airborne. By ending a dialogue will Ammy snap back to the ground. One can also air tackle into a slope to regain a grounded state, which also allows you to gain height. Otherwise, Ammy is height-locked. This no-clip state is retained even across loading zones, unlike WWT itself.
Hypothetically, this could allow for major sequence breaks, but the long, precise setup and under-explored mechanics have prevented its implementation into speedruns.
Tsuta
In the poison pot room, it is possible to perform a Brush Adventure up to the ledge where the poison pots, but before all 3 devil gates have been defeated. Though the pots are invisible and cannot be attacked or PS'd, their hitboxes can still be hit by CB's. If all of the pots are destroyed using CB's, then the mushroom growing cutscene is triggered and allowed to play out, you will have WWT. See https://youtu.be/5Wjfv3Bg0-o. This also has the effect of removing the loading zone to the Vine room.
Kusa
In cursed Kusa (i.e. before talking to Fuse), whenever Ammy attempts to use the brush, Issun will talk as soon as the brush closes. You can interrupt Issun's dialogue by talking to the merchant at the entrance of the village, then tackle his shop and talk a few times to bring up the shopping yes-no menu. This menu can be taken through the village without crashing. Because the only way to progress in cursed Kusa is to completely talk to Fuse, cancelling WWT, this has no use. It is, however, likely the easiest and fastest way to demonstrate WWT.
Sei-an Aristocratic
If a day-night transition is queued up to happen just as one exits the Eastern treasure room in Himiko's Palace after entering it through Rao's secret tunnel for the first time, the day-night cutscene will interrupt Issun's text. This can be done via an interior clip out of the treasure room and into Rao's tunnel. See https://streamable.com/zrsch.
Unfortunately, due to the lack of any animals to feed in Sei-an Aristocratic, no-clip cannot be apparently be performed here.