When the pressure is not changed smoothly in a stroke, the brush density curve is changed. 一筆で滑らかに筆圧が変えられない時はブラシ濃度のカーブを変えます。
It is close to the brush of the behavior that is apt to look good on other software and free drawing site (the basic brush setting is a little workin'.)
■ Basic brush ■
Mix and transparent, the concentration changes with the pressure when I drew it by a stroke writing
■ T-20% brush ■
The concentration does not change even if the pressure is changed when drawing by the mix, transmitting, and the stroke writing.
■ 20% brush ■
The concentration does not change even if I change the pressure when I draw the same color and a stroke writing even if I do not mix, and do not transmit it.
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★ Basic Brushes
I compared it with a main paint software.

※ SAI is not very familiar, but when the start of the brush is white, the color is slightly different because it is like a drag on the movement.
※ The default watercolor brush of the clip studio, even if I put a strong pressure, I think the behavior does not thicken until the color of the main color, this brush becomes. It is necessary to change the pressure curve of the concentration in the one that a little brush pressure control is needed, and it becomes dense suddenly.
★ T-20% Brush, 20% brush

他ソフトや無料お絵かきサイトで良く見がちな挙動の筆に近づけてます(基本のブラシ設定を少し弄っただけです)
■基本筆■
混ざらない、透過する、一筆書きで描いた際に筆圧で濃度が変わる
■t-20%ブラシ■
混ざらない、透過する、一筆書きで描いた際筆圧を変えても濃度は変わらない
■20%ブラシ■
混ざらない、透過しないで重ねても同じ色、一筆書きで描いた際筆圧を変えても濃度は変わらない
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★基本筆
主なペイントソフトで比べてみました

※SAIはあまり詳しくないのですが、ブラシの開始が白の場合は引きずらなく色は引きずる様な挙動なので少し違います。
※クリップスタジオのデフォルトの水彩筆は強く筆圧をかけても、メインカラーの色までは濃くはならない挙動だと思うのですが、この筆はなります。ただ多少のブラシ筆圧コントロールは必要で、いきなり濃くなってしまうーという方は濃度の筆圧曲線を変えてみて下さい。
★t-20%ブラシ、20%ブラシ

Brush ブラシ