My senior brother is too steady is a Manga/Manhwa/Manhua in (English/Raw) language, Action series, english chapters have been translated and you can read them here.
The Summary is
After being reborn in ancient times before the Great God-Conferment War, Li Changshou became a small cultivator.
To survive in the cruel Primordial Times, Li Changshou tries hard not to accumulate any karma. He always plans thoroughly before doing anything and never allows himself to walk into dangerous situations. He hides his trump cards well, trains himself in escape techniques, refines poisonous pills, and masters mystical abilities.
Li Changshou originally planned to remain hidden and safe in the mountain until his ascension to immortality. However, everything changed one year when his master brought home a junior sister…