雁字搦め(がんじがらめ) describes being bound or trapped so tightly that you cannot move freely. It can refer to physical restraints, but in this song it is used metaphorically for feeling shackled by everyday life and later being emotionally entangled with someone.
The unusual kanji and vivid image make it especially memorable for learners. The phrase captures the song's sense of being overwhelmed and unable to break free.
"Overflow" is King Gnu at their most frantic and honest. The narrator starts by shrugging off the big questions, admitting he doesn't know what happiness costs and doesn't even want to know, then turns on himself with a blunt reality check: "自分の替えなど" (someone to replace me) "いくらでもいるんだ" (there are plenty of them), followed by "自惚れんなよ" (don't get full of yourself). That last one is the kind of thing a friend snaps at you, and it's a useful phrase to learn: 自惚れる means to be conceited, and the casual negative command んなよ makes it sound like a real scolding. He's burning through life "ガムシャラに" (recklessly, with everything he's got) and swinging a blade around at random, and the chorus explains why: "オーバーフローしているんだ" (I'm overflowing) and "日々に雁字搦めなんだ" (I'm tied up tight by my days). 雁字搦め is a great idiom to pick up. It literally means being bound up in knots, and here it's the feeling of a schedule that won't let you breathe.
The fix he lands on is simple: go find love, go see you, before "臆病風になびいてしまう前に" (before I give in to cowardice). 臆病風 is literally a "coward's wind," something that blows you off course. Then comes my favourite stretch, a run of pleading requests: "みっともないって呆れてくれよ" (go ahead, be fed up and call me pathetic), "惨めだねって罵ってくれよ" (go ahead, curse me as miserable), and finally "昔みたいに笑ってくれよ" (just laugh with me like you used to). He'd rather be insulted by this person than lose them, which is a bit much and also very relatable. Watch for "脳味噌オフ" (brain switched off), a funny slangy mix of 脳味噌 (brains, the squishy kind) and the English "off," right before he admits he's spiralling into a messy fight. The song ends on a quiet confession: he only has a handful of things that really matter, and without noticing he got far too greedy.