Previously in Berserk chapter 325 the Merrows launched their song attack at the great Sea God as Gutts struggled to stay alive.
The merrows' song attack is proving to be super effective. The sea god starts flopping about and and shooting water from it's blow hole. Inside, Gutts is still incapacitated with Shrieke begging him to move. The song seems to have interrupted the sonic boom of the Sea God's heartbeat giving him a chance to strike. However, you know...he still can't move.
After tapping into his inner wild dog (his suit) Gutts gets the strength to get up. He's still blind so Shrieke has to guide him to the heart. With one mighty swing of his sword, he cleaves into the heart of the God.
The God spews vomit and begins to deflate and sink.
Everyone is joyous in their victory, even if it was very anticlimactic. Shrieke comes to and the chapters ends on a cliff hanger of everyone wondering where the hell Gutts is.
Again, Evil Genius is still down, so here is where I read this online.