Use an Array Modifier with an "object offset" (using an empty) to create a tapering effect where the tail gets thinner toward the end.

Use procedural motor systems to automate the "wavy" idle animation of long tentacle chains. 3. Anime-Specific Animation Techniques

Use the Puppet Position Tool to place pins along a straight tentacle illustration.

The movement of tentacles is typically achieved through specialized rigging rather than standard limb armatures. 3D Workflow (Blender)

Before animating, define the scene's and layers.

To achieve a professional "anime" look, apply these stylistic principles: How I Animate a Scene from Beginning to End