senpai_(tawawa)
A character from Getsuyoubi no Tawawa. Kouhai-chan's senior coworker, who is also her unofficial self-appointed guardian from those who seek to exploit her when she's off-guard, especially when she's drunk.
His protectiveness becomes a factor in him bonding with Kouhai-chan's college friend Rikei-chan (post #3622784), as she "used to do the same thing":/posts/3256706 back in the day.
His name is written 先パイ, which is a pun on 先輩 ("senior, upperclassman") by way of how the second kanji is pronounced identically to the second half of オッパイ (oppai, meaning "breasts").