Template.tex

\usepackage{xcolor}
\definecolor{Sumire}{RGB}{102,50,124}
\definecolor{Shion}{RGB}{143,119,181}

\usepackage{titlesec}
\usepackage{titleps}
\usepackage{tikz}
\usetikzlibrary{arrows.meta}


\newcommand{\chapnumfont}{%
	\fontsize{100}{100}\usefont{T1}{ptm}{b}{n}%
}

\colorlet{chapbgcolor}{gray!75}
\colorlet{chapnumcolor}{black!60}


\newcommand{\chaptitlenumbered}[1]{%
	\begin{tikzpicture}
	\fill[chapbgcolor!70,rounded corners=0pt] (0,2.3) rectangle (\linewidth,0);
	\node[
	align=right,
	anchor=south east,
	inner sep=8pt,
	font=\huge\normalfont\bfseries
	] at (0.987\linewidth,0) {\strut#1};
	\node[
	align=right,
	font=\fontsize{60}{62}\usefont{OT1}{ptm}{b}{it},
	text=chapnumcolor
	] at (0.975\linewidth,2.3) {\thechapter};
	\end{tikzpicture}%
}

\newcommand{\chaptitleunnumbered}[1]{%
	\begin{tikzpicture}
	\fill[chapbgcolor!70,rounded corners=0pt] (0,2.3) rectangle (\linewidth,0);
	\node[
	align=right,
	anchor=south east,
	inner sep=8pt,
	font=\huge\normalfont\bfseries
	] at (0.987\linewidth,0) {\strut#1};
	\end{tikzpicture}%
}

\usepackage{titlesec}

\titleformat{name=\chapter}[display]
{\normalfont\huge\bfseries\sffamily}
{}
{40pt}
{\chaptitlenumbered}
\titleformat{name=\chapter,numberless}[display]
{\normalfont\huge\bfseries\sffamily}
{}
{25pt}
{\chaptitleunnumbered}
\titlespacing*{\chapter}
{0pt}
{-126pt}
{33pt}

\titleformat{\section}
{\normalfont\centering\zihao{4}\bfseries}
{{\mdseries\S}\ \thesection}{.5em}{}

\setlength\headheight{15pt}

\usepackage{dsfont}

\renewcommand{\baselinestretch}{1.5}

\renewcommand\sectionmark[1]{%
	\markright{\thesection\quad #1}}