The storyboard (絵コンテ, ekonte) is the visual representation of the animation sequence by scene. You can think of it as the earliest and roughest plan for how the anime episode or movie will eventually look like.
Generally, full storyboard sheets are extremely important as they outline the key scenes in each anime, and include information on dialogue, music, sound effects and camera work which will inform the rest of production.
Storyboarding is usually done in pre-production after the script is written. It is typically done by the director (監督, kantoku) or Unit Director (演出, enshutsu).
The look of storyboards can also vary greatly. Some directors are well known for extremely detailed storyboards, while others may draw some that resemble nothing more than haphazard scribbles.
For the DenDekaDen PV, storyboarding was handled by director Masatsugu Nagasoe (who also worked on season 1 Ending of Jujutsu Kaisen!)
絵コンテは、シナリオをもとに制作されたアニメーションにおける映像設計図です。画面の構図やキャラクターの演技内容、カメラワーク、セリフ、SEなどの演出指示がイラストとともに記されており、アニメ制作スタッフが作業方針を共有する目的で作成されます。
通常、監督か演出（絵コンテマン）が担当し、緻密に描く人もいればイラストメインの感覚的な絵コンテを描く人もいて担当者によって様々です。
『電殿神伝』のPVは長添雅嗣監督（呪術廻戦 第1期エンディングを担当）が絵コンテを担当しています。
Character Design (キャラクターデザイン, kyarakutā dezain) is a process which the Character Designer (キャラクターデザイナー, kyarakutā dezainā) aims to express the unique worldview of the work, such as the world’s culture, through the eyes of the characters. This is an extensive process that is based on the script, as well as the feedback from the director and the original creator.